#include<bits/stdc++.h>
using namespace std;

const int N = 1 << 21;
const int mod = 998244353;
const int root = 3;
int lim, rev[N], w[N], wn[N], inv_lim;
void reduce(int &x) { x = (x + mod) % mod; }
int POW(int x, int y, int ans = 1) {
  for (; y; y >>= 1, x = (long long) x * x % mod) if (y & 1) ans = (long long) ans * x % mod;
  return ans;
}
void precompute(int len) {
  lim = wn[0] = 1; int s = -1;
  while (lim < len) lim <<= 1, ++s;
  for (int i = 0; i < lim; ++i) rev[i] = rev[i >> 1] >> 1 | (i & 1) << s;
  const int g = POW(root, (mod - 1) / lim);
  inv_lim = POW(lim, mod - 2);
  for (int i = 1; i < lim; ++i) wn[i] = (long long) wn[i - 1] * g % mod;
}
void ntt(vector<int> &a, int typ) {
  for (int i = 0; i < lim; ++i) if (i < rev[i]) swap(a[i], a[rev[i]]);
  for (int i = 1; i < lim; i <<= 1) {
    for (int j = 0, t = lim / i / 2; j < i; ++j) w[j] = wn[j * t];
    for (int j = 0; j < lim; j += i << 1) {
      for (int k = 0; k < i; ++k) {
        const int x = a[k + j], y = (long long) a[k + j + i] * w[k] % mod;
        reduce(a[k + j] += y - mod), reduce(a[k + j + i] = x - y);
      }
    }
  }
  if (!typ) {
    reverse(a.begin() + 1, a.begin() + lim);
    for (int i = 0; i < lim; ++i) a[i] = (long long) a[i] * inv_lim % mod;
  }
}
vector<int> multiply(vector<int> &f, vector<int> &g) {
  int n=(int)f.size() + (int)g.size() - 1;
  precompute(n);
  vector<int> a = f, b = g;
  a.resize(lim); b.resize(lim);
  ntt(a, 1), ntt(b, 1);
  for (int i = 0; i < lim; ++i) a[i] = (long long) a[i] * b[i] % mod;
  ntt(a, 0);
  return a;
}
template <const int32_t MOD>
struct modint {
  int32_t value;
  modint() = default;
  modint(int32_t value_) : value(value_) {}
  inline modint<MOD> operator + (modint<MOD> other) const { int32_t c = this->value + other.value; return modint<MOD>(c >= MOD ? c - MOD : c); }
  inline modint<MOD> operator - (modint<MOD> other) const { int32_t c = this->value - other.value; return modint<MOD>(c <    0 ? c + MOD : c); }
  inline modint<MOD> operator * (modint<MOD> other) const { int32_t c = (int64_t)this->value * other.value % MOD; return modint<MOD>(c < 0 ? c + MOD : c); }
  inline modint<MOD> & operator += (modint<MOD> other) { this->value += other.value; if (this->value >= MOD) this->value -= MOD; return *this; }
  inline modint<MOD> & operator -= (modint<MOD> other) { this->value -= other.value; if (this->value <    0) this->value += MOD; return *this; }
  inline modint<MOD> & operator *= (modint<MOD> other) { this->value = (int64_t)this->value * other.value % MOD; if (this->value < 0) this->value += MOD; return *this; }
  inline modint<MOD> operator - () const { return modint<MOD>(this->value ? MOD - this->value : 0); }
  modint<MOD> pow(uint64_t k) const { modint<MOD> x = *this, y = 1; for (; k; k >>= 1) { if (k & 1) y *= x; x *= x; } return y; }
  modint<MOD> inv() const { return pow(MOD - 2); }  // MOD must be a prime
  inline modint<MOD> operator /  (modint<MOD> other) const { return *this *  other.inv(); }
  inline modint<MOD> operator /= (modint<MOD> other)       { return *this *= other.inv(); }
  inline bool operator == (modint<MOD> other) const { return value == other.value; }
  inline bool operator != (modint<MOD> other) const { return value != other.value; }
  inline bool operator < (modint<MOD> other) const { return value < other.value; }
  inline bool operator > (modint<MOD> other) const { return value > other.value; }
};
template <int32_t MOD> modint<MOD> operator * (int64_t value, modint<MOD> n) { return modint<MOD>(value) * n; }
template <int32_t MOD> modint<MOD> operator * (int32_t value, modint<MOD> n) { return modint<MOD>(value % MOD) * n; }
template <int32_t MOD> istream & operator >> (istream & in, modint<MOD> &n) { return in >> n.value; }
template <int32_t MOD> ostream & operator << (ostream & out, modint<MOD> n) { return out << n.value; }

using mint = modint<mod>;

struct Combi{
  int n; vector<mint> facts, finvs, invs;
  Combi(int _n): n(_n), facts(_n), finvs(_n), invs(_n){
    facts[0] = finvs[0] = 1;
    invs[1] = 1;
      for (int i = 2; i < n; i++) invs[i] =  invs[mod % i] * (-mod / i);
    for(int i = 1; i < n; i++){
      facts[i] = facts[i - 1] * i;
      finvs[i] = finvs[i - 1] * invs[i];
    }
  }
  inline mint fact(int n) { return facts[n]; }
  inline mint finv(int n) { return finvs[n]; }
  inline mint inv(int n) { return invs[n]; }
  inline mint ncr(int n, int k) { return n < k ? 0 : facts[n] * finvs[k] * finvs[n-k]; }
};
Combi C(N);

vector<int> power(vector<int> f, int n) {
  auto ans = f;
  n--;
  while (n) {
    if (n & 1) ans = multiply(ans, f);
    f = multiply(f, f);
    n >>= 1;
  }
  return ans;
}
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, m; cin >> n >> m;
  vector<int> f(m + 1);
  for (int k = 0; k <= m; k++) {
    f[k] = (C.ncr(m, k) * C.ncr(m, k) * C.fact(k)).value;
  }
  auto a = power(f, n);
  mint ans = 0;
  for (int i = 0; i <= n * m; i++) {
    ans += 1LL * (i & 1 ? mod - 1 : 1) * a[i] % mod * C.fact(n * m - i);
  }
  cout << ans << '\n';
  return 0;
}

answer.code: In function ‘int32_t main()’:
answer.code:114:53: error: ambiguous overload for ‘operator*’ (operand types are ‘long long int’ and ‘mint’ {aka ‘modint<998244353>’})
  114 |     ans += 1LL * (i & 1 ? mod - 1 : 1) * a[i] % mod * C.fact(n * m - i);
      |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~
      |                                               |             |
      |                                               long long int mint {aka modint<998244353>}
answer.code:68:36: note: candidate: ‘modint<MOD> operator*(int64_t, modint<MOD>) [with int MOD = 998244353; int64_t = long int]’
   68 | template <int32_t MOD> modint<MOD> operator * (int64_t value, modint<MOD> n) { return modint<MOD>(value) * n; }
      |                                    ^~~~~~~~
answer.code:69:36: note: candidate: ‘modint<MOD> operator*(int32_t, modint<MOD>) [with int MOD = 998244353; int32_t = int]’
   69 | template <int32_t MOD> modint<MOD> operator * (int32_t value, modint<MOD> n) { return modint<MOD>(value % MOD) * n; }
      |                                    ^~~~~~~~