#include <cstdio>

using LL = long long;
const int N = 1000 + 5;
const int M = 12;
const int Mod = 998244353;

inline int qp(int a, int b = Mod - 2) {
  int res = 1;
  while (b) {
    if (b & 1) res = LL(res) * a % Mod;
    a = LL(a) * a % Mod;
    b /= 2;
  }
  return res;
}

int fac[N], ifac[N], iv[N];
inline void initComb(int n) {
  fac[0] = 1;
  for (int i = 1; i <= n; ++i) fac[i] = LL(fac[i - 1]) * i % Mod;
  ifac[n] = qp(fac[n]);
  for (int i = n; i; --i) ifac[i - 1] = LL(ifac[i]) * i % Mod;
  for (int i = 1; i <= n; ++i) iv[i] = qp(i);
}
inline int binom(int n, int m) {
  if (n < m || m < 0) return 0;
  return LL(fac[n]) * ifac[n - m] % Mod * ifac[m] % Mod;
}

int n, m, sb;
int a[N], b[N], c[N];
int f[N][1 << M], g[N][1 << M];

int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < m; ++i) scanf("%d", &a[i]);
  for (int i = 0; i < m; ++i) scanf("%d", &b[i]), sb += b[i];
  initComb(n);
  int beg = 0;
  for (int i = 0; i < m; ++i)
    if (!b[i]) beg |= (1 << i);
  g[0][beg] = 1;
  for (int i = 0; i < m; ++i) {
    c[i] = 1;
    for (int j = 1; j <= b[i]; ++j) c[i] = LL(c[i]) * (a[i] - j + 1) % Mod;
  }
  for (int s = beg + 1; s < (1 << m); ++s) {
    if ((s & beg) != beg) continue;
    for (int x = 0; x < m; ++x) if (s >> x & 1 && b[x]) {
      int t = s - (1 << x), sum = 0, lim = 0;
      for (int i = 0; i < m; ++i) if (t >> i & 1)
        sum += a[i] - b[i], lim += b[i];
      int sg = 0, sf1 = 0, sf2 = 0;
      for (int i = 0; i <= sb; ++i) {
        if (i > lim) {
          int tmp = LL(c[x]) * binom(i - 1 - lim, b[x] - 1) % Mod;
          (f[i][s] += LL(sf1 + sf2) * tmp % Mod) %= Mod;
          (g[i][s] += LL(sg) * tmp % Mod) %= Mod;
        }
        (sf1 += f[i][t]) %= Mod;
        (sg += g[i][t]) %= Mod;
        (sf2 += LL(sg) * iv[n - i - sum] % Mod * sum % Mod) %= Mod;
        sf1 = LL(sf1) * iv[n - i - sum] % Mod;
        sf2 = LL(sf2) * iv[n - i - sum] % Mod;
        sg = LL(sg) * iv[n - i - sum] % Mod;
      }
    }
  }
  printf("%d\n", (sb + f[sb][(1 << m) - 1]) % Mod);
  return 0;
}