#include <bits/stdc++.h>

/**
 * Author: Niyaz Nigmatullin
 *
 */

using namespace std;

string to_string(string s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T>
T inverse(T a, T m) {
  assert(a != 0);
  T u = 0, v = 1;
  while (a != 0) {
    T t = m / a;
    m -= t * a; swap(a, m);
    u -= t * v; swap(u, v);
  }
  assert(m == 1);
  return u;
}

template <typename T>
class Modular {
 public:
  using Type = typename decay<decltype(T::value)>::type;

  constexpr Modular() : value() {}
  template <typename U>
  Modular(const U& x) {
    value = normalize(x);
  }

  template <typename U>
  static Type normalize(const U& x) {
    Type v;
    if (-mod() <= x && x < mod()) v = static_cast<Type>(x);
    else v = static_cast<Type>(x % mod());
    if (v < 0) v += mod();
    return v;
  }

  const Type& operator()() const { return value; }
  template <typename U>
  explicit operator U() const { return static_cast<U>(value); }
  constexpr static Type mod() { return T::value; }

  Modular& operator+=(const Modular& other) { if ((value += other.value) >= mod()) value -= mod(); return *this; }
  Modular& operator-=(const Modular& other) { if ((value -= other.value) < 0) value += mod(); return *this; }
  template <typename U> Modular& operator+=(const U& other) { return *this += Modular(other); }
  template <typename U> Modular& operator-=(const U& other) { return *this -= Modular(other); }
  Modular& operator++() { return *this += 1; }
  Modular& operator--() { return *this -= 1; }
  Modular operator++(int) { Modular result(*this); *this += 1; return result; }
  Modular operator--(int) { Modular result(*this); *this -= 1; return result; }
  Modular operator-() const { return Modular(-value); }

  template <typename U = T>
  typename enable_if<is_same<typename Modular<U>::Type, int>::value, Modular>::type& operator*=(const Modular& rhs) {
#ifdef _WIN32
    uint64_t x = static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value);
    uint32_t xh = static_cast<uint32_t>(x >> 32), xl = static_cast<uint32_t>(x), d, m;
    asm(
      "divl %4; \n\t"
      : "=a" (d), "=d" (m)
      : "d" (xh), "a" (xl), "r" (mod())
    );
    value = m;
#else
    value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
#endif
    return *this;
  }
  template <typename U = T>
  typename enable_if<is_same<typename Modular<U>::Type, int64_t>::value, Modular>::type& operator*=(const Modular& rhs) {
    int64_t q = static_cast<int64_t>(static_cast<long double>(value) * rhs.value / mod());
    value = normalize(value * rhs.value - q * mod());
    return *this;
  }
  template <typename U = T>
  typename enable_if<!is_integral<typename Modular<U>::Type>::value, Modular>::type& operator*=(const Modular& rhs) {
    value = normalize(value * rhs.value);
    return *this;
  }

  Modular& operator/=(const Modular& other) { return *this *= Modular(inverse(other.value, mod())); }

  template <typename U>
  friend bool operator==(const Modular<U>& lhs, const Modular<U>& rhs);

  template <typename U>
  friend bool operator<(const Modular<U>& lhs, const Modular<U>& rhs);

  template <typename U>
  friend std::istream& operator>>(std::istream& stream, Modular<U>& number);

 private:
  Type value;
};

template <typename T> bool operator==(const Modular<T>& lhs, const Modular<T>& rhs) { return lhs.value == rhs.value; }
template <typename T, typename U> bool operator==(const Modular<T>& lhs, U rhs) { return lhs == Modular<T>(rhs); }
template <typename T, typename U> bool operator==(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) == rhs; }

template <typename T> bool operator!=(const Modular<T>& lhs, const Modular<T>& rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(const Modular<T>& lhs, U rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(U lhs, const Modular<T>& rhs) { return !(lhs == rhs); }

template <typename T> bool operator<(const Modular<T>& lhs, const Modular<T>& rhs) { return lhs.value < rhs.value; }

template <typename T> Modular<T> operator+(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) += rhs; }
template <typename T, typename U> Modular<T> operator+(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) += rhs; }

template <typename T> Modular<T> operator-(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) -= rhs; }
template <typename T, typename U> Modular<T> operator-(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) -= rhs; }

template <typename T> Modular<T> operator*(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) *= rhs; }
template <typename T, typename U> Modular<T> operator*(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) *= rhs; }

template <typename T> Modular<T> operator/(const Modular<T>& lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(const Modular<T>& lhs, U rhs) { return Modular<T>(lhs) /= rhs; }
template <typename T, typename U> Modular<T> operator/(U lhs, const Modular<T>& rhs) { return Modular<T>(lhs) /= rhs; }

template<typename T, typename U>
Modular<T> power(const Modular<T>& a, const U& b) {
  assert(b >= 0);
  Modular<T> x = a, res = 1;
  U p = b;
  while (p > 0) {
    if (p & 1) res *= x;
    x *= x;
    p >>= 1;
  }
  return res;
}

template <typename T>
string to_string(const Modular<T>& number) {

for (int i = 1; i < 100; i++) {
	if ((int) (number * i) < 1000) return to_string((int) (number * i)) + "/" + to_string(i);
}
  return to_string(number());
}

template <typename T>
std::ostream& operator<<(std::ostream& stream, const Modular<T>& number) {
  return stream << number();
}

template <typename T>
std::istream& operator>>(std::istream& stream, Modular<T>& number) {
  typename common_type<typename Modular<T>::Type, int64_t>::type x;
  stream >> x;
  number.value = Modular<T>::normalize(x);
  return stream;
}

/*
using ModType = int;

struct VarMod { static ModType value; };
ModType VarMod::value;
ModType& md = VarMod::value;
using Mint = Modular<VarMod>;
*/

constexpr int md = 998244353;
using Mint = Modular<std::integral_constant<decay<decltype(md)>::type, md>>;

Mint solve(int n, vector<int> const &a, vector<int> const &b) {
	int m = (int) a.size();
	vector<vector<Mint>> f(1 << m, vector<Mint>(n + 1));
	f[0][0] = 1;
	vector<vector<Mint>> ff(1 << m, vector<Mint>(n + 1));
	ff[0][0] = 1;
	vector<vector<Mint>> c(n + 1, vector<Mint>(n + 1));
	for (int i = 0; i <= n; i++) {
		c[i][0] = 1;
		for (int j = 1; j <= i; j++) {
			c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
		}
	}
	for (int mask = 1; mask < (1 << m); mask++) {
		int any = 0;
		while (((mask >> any) & 1) == 0) ++any;
		// f[mask & ~(1 << any)], any
		int without = mask & ~(1 << any);
		for (int was = 0; was <= n; was++) {
			Mint numerator = 1;
			for (int get = 0; get + was <= n && get <= b[any]; get++) {
				numerator *= a[any] - get;
				ff[mask][get + was] += ff[without][was] * c[get + was][get] * numerator;
			}
			Mint value = f[without][was];
			if (value == 0) continue;
			numerator = 1;
			for (int get = 0; get + was <= n && get < b[any]; get++) {
				numerator *= a[any] - get;
				f[mask][get + was] += value * c[get + was][get] * numerator;
			}
		}
	}
	for (int mask = 0; mask < 1 << m; mask++) {
		for (int i = 0; i < m; i++) {
			if (((mask >> i) & 1) == 0) {
				Mint numerator = 1;
				for (int j = 0; j < b[i]; j++) {
					numerator *= a[i] - j;
				}
				for (int was = n - b[i]; was >= 0; was--) {
					f[mask][was + b[i]] += f[mask][was] * c[was + b[i]][b[i]] * numerator;
				}
			}
		}
	}
	int targetSum = 0;
	for (int x: b) targetSum += x;
	vector<int> sumB(1 << m);
	vector<int> sumA(1 << m);
	for (int mask = 0; mask < 1 << m; mask++) {
		for (int i = 0; i < m; i++) {
			if ((mask >> i) & 1) {
				sumB[mask] += b[i];
				sumA[mask] += a[i];
			}
		}
	}
	// vector<vector<Mint>> g(1 << m, vector<Mint>(targetSum + 1));
	// g[(1 << m) - 1][targetSum] = 0;
	// for (int mask = (1 << m) - 2; mask >= 0; mask--) {
	// 	for (int k = targetSum - 1; k >= sumB[mask]; k--) {
	// 		Mint sumAddBit = 0;
	// 		int left = k - sumB[mask];
	// 		Mint good = Mint(n) - Mint(sumA[mask]) - Mint(left);
	// 		Mint bad = sumA[mask] - sumB[mask];
	// 		// debug(good);
	// 		Mint expected = (good + bad) / good;
	// 		Mint allWays = f[((1 << m) - 1) ^ mask][left];
	// 		if (allWays == 0) continue;
	// 		for (int i = 0; i < m; i++) {
	// 			if (((mask >> i) & 1) == 1) continue;
	// 			if (left < b[i] - 1) continue;
	// 			Mint goodWays = f[((1 << m) - 1) ^ mask ^ (1 << i)][left - (b[i] - 1)] * c[left][b[i] - 1];
	// 			// debug(good);
	// 			Mint prob = goodWays / allWays * (a[i] - (b[i] - 1)) / good;
	// 			sumAddBit += prob;
	// 			g[mask][k] += (g[mask | (1 << i)][k + 1] + expected) * prob;
	// 		}
	// 		Mint probStay = 1 - sumAddBit;
	// 		g[mask][k] += (g[mask][k + 1] + expected) * probStay;
	// 		debug(mask, k, g[mask][k]);
	// 	}
	// }
	Mint answer = 0;
	for (int mask = (1 << m) - 2; mask >= 0; mask--) {
		for (int k = sumB[mask]; k < targetSum; k++) {
			int left = k - sumB[mask];
			int good = n - sumA[mask] - left;
			Mint denominator = 1;
			for (int i = 0; i < k; i++) {
				denominator *= good - i;
			}
			int bad = sumA[mask] - sumB[mask];
			// debug(good);
			Mint expected = Mint(good + bad) / good;
			Mint goodWays = f[((1 << m) - 1) ^ mask][left];
			for (int i = 0, count = left; i < m; i++) {
				if (((mask >> i) & 1) == 1) {
					goodWays *= c[count + b[i]][b[i]];
					count += b[i];
				}
			}
			Mint allWays = ff[((1 << m) - 1)][k];
			debug(mask, k, goodWays, allWays, expected);
			answer += goodWays / allWays * expected;
		}
	}
	// return g[0][0];
	return answer;
}


Mint solve2(int n, vector<int> a, vector<int> b) {
	int m = (int) a.size();
	vector<vector<Mint>> f(1 << m, vector<Mint>(n + 1));
	f[0][0] = 1;
	vector<vector<Mint>> c(n + 1, vector<Mint>(n + 1));
	for (int i = 0; i <= n; i++) {
		c[i][0] = 1;
		for (int j = 1; j <= i; j++) {
			c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
		}
	}
	for (int mask = 1; mask < (1 << m); mask++) {
		int any = 0;
		while (((mask >> any) & 1) == 0) ++any;
		// f[mask & ~(1 << any)], any
		int without = mask & ~(1 << any);
		for (int was = 0; was <= n; was++) {
			Mint value = f[without][was];
			if (value == 0) continue;
			for (int get = 0; get + was <= n && get < b[any]; get++) {
				f[mask][get + was] += value * c[get + was][get];
				value *= a[any] - get;
			}
		}
	}
	int targetSum = 0;
	for (int x: b) targetSum += x;
	vector<int> sumB(1 << m);
	vector<int> sumA(1 << m);
	for (int mask = 0; mask < 1 << m; mask++) {
		for (int i = 0; i < m; i++) {
			if ((mask >> i) & 1) {
				sumB[mask] += b[i];
				sumA[mask] += a[i];
			}
		}
	}
	vector<vector<Mint>> fDen(1 << m, vector<Mint>(targetSum + 1));
	vector<Mint> fullNumerator(m);
	for (int i = 0; i < m; i++) {
		fullNumerator[i] = 1;
		for (int j = 0; j < b[i]; j++) {
			fullNumerator[i] *= a[i] - j;
		}
	}
	int initMask = 0;
	for (int i = 0; i < m; i++) {
		if (b[i] == 0) initMask |= 1 << i;
	}
	fDen[initMask][0] = 1;
	for (int mask = 0; mask < 1 << m; mask++) {
		for (int count = sumB[mask]; count < targetSum; count++) {
			Mint value = fDen[mask][count];
			if (value == 0) continue;
			int ways = (n - sumA[mask]) - (count - sumB[mask]);
			if (ways == 0) continue;
			value /= ways;
			for (int i = 0; i < m; i++) {
				if (((mask >> i) & 1) == 0 && count + 1 >= sumB[mask] + b[i]) {
					fDen[mask | (1 << i)][count + 1] += value * c[count - sumB[mask]][b[i] - 1] * fullNumerator[i];
				}
			}
			fDen[mask][count + 1] += value;
		}
	}
	Mint answer = 0;
	for (int mask = 0; mask + 1 < 1 << m; mask++) {
		for (int k = sumB[mask]; k < targetSum; k++) {
			int left = k - sumB[mask];
			int good = n - sumA[mask] - left;
			int bad = sumA[mask] - sumB[mask];
			Mint expected = Mint(good + bad) / good;
			Mint prob = f[((1 << m) - 1) ^ mask][left] * fDen[mask][k];
			answer += prob * expected;
		}
	}
	// return g[0][0];
	return answer;
}

struct state {
	vector<int> taken;

	bool operator==(state const &s) const {
		return s.taken == taken;
	}
};

namespace std {
	template<>
	struct hash<state> {
		size_t operator()(state const &s) const {
			size_t h = 0;
			for (int x : s.taken) {
				h = h * 239017 + x + 1;
			}
			return h;
		}
	};
};

string to_string(state const &s) {
	return to_string(s.taken);
}

Mint solveStupid(int n, vector<int> const &a, vector<int> const &b) {
	unordered_map<state, Mint> expected;
	expected[{b}] = 0;
	int m = (int) a.size();
	Mint ans2 = 0;
	function<Mint(state const &, Mint)> calc = [&](state const &s, Mint prob) {
		// if (expected.find(s) != expected.end()) {
		// 	return expected[s];
		// }
		if (s.taken == b) {
			return Mint(0);
		}
		int ways = 0;
		int allWays = 0;
		for (int i = 0; i < m; i++) {
			if (s.taken[i] < b[i]) {
				ways += a[i] - s.taken[i];
			}
			allWays += a[i] - s.taken[i];
		}
		Mint res = Mint(allWays) / Mint(ways);
		ans2 += prob * Mint(allWays) / Mint(ways);
		debug(s, prob, Mint(allWays) / Mint(ways));
		for (int i = 0; i < m; i++) {
			if (s.taken[i] < b[i]) {
				state ns = s;
				ns.taken[i]++;
				Mint got = calc(ns, prob * Mint(a[i] - s.taken[i]) / Mint(ways));
				res += got * Mint(a[i] - s.taken[i]) / ways;
			}
		}
		return expected[s] = res;
	};
	Mint res = calc({vector<int>(m, 0)}, 1);
	debug(expected);
	debug(res, ans2);
	return res;
}

void stress() {
	mt19937 rng(239);
	for (int it = 0; it < 10000; it++) {
		int n = 5;
		vector<int> a(n), b(n);
		for (int i = 0; i < n; i++) {
			b[i] = rng() % 2 + 1;
			a[i] = b[i] + rng() % 3;
		}
		int sum = accumulate(a.begin(), a.end(), 0);
		Mint ans1 = solve2(sum, a, b);
		Mint ans2 = solveStupid(sum, a, b);
		if (ans1 != ans2) {
			debug(a, b);
			debug(ans1, ans2);
			assert(ans1 == ans2);
		}
	}

}

int main() {
	std::cin.tie(NULL); std::ios::sync_with_stdio(false);
	// stress();
	int n, m;
	cin >> n >> m;
	vector<int> a(m);
	for (int &x: a) cin >> x;
	vector<int> b(m);
	for (int &x: b) cin >> x;
	Mint ans = solve2(n, a, b);
	// Mint ans2 = solveStupid(n, a, b);
	// for (int i = 1; i < 100; i++) {
	// 	if ((int) (ans * i) < 1000) {
	// 		cout << ans * i << '/' << i << endl;
	// 		break;
	// 	}
	// }
	// debug(ans);
	cout << ans << '\n';
}