#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int G = 3;
const int MOD = 998244353;
const int N = (1 << 20) + 5;

int rev[N], w[N], inv_n;

ll bigMod (ll a, ll e) {
  if (e == -1) e = MOD - 2;
  ll ret = 1;
  while (e) {
    if (e & 1) ret = ret * a % MOD;
    a = a * a % MOD, e >>= 1;
  }
  return ret;
}

void prepare (int n) { 
  int tot = abs(31 - __builtin_clz(n));
  int r = bigMod(G, (MOD - 1) / n); 
  inv_n = bigMod(n, -1), w[0] = w[n] = 1; 
  for (int i = 1; i < n; ++i) w[i] = (ll) w[i - 1] * r % MOD;
  for (int i = 1; i < n; ++i) rev[i] = (rev[i >> 1] >> 1) | ((i & 1) << (tot - 1));
}

void ntt (int *a, int n, int dir) { 
  for (int i = 1; i < n - 1; ++i) { 
    if (i < rev[i]) swap(a[i], a[rev[i]]);
  }
  for (int m = 2; m <= n; m <<= 1) {
    for (int i = 0; i < n; i += m) {
      for (int j = 0; j < (m >> 1); ++j) {
        int &u = a[i + j], &v = a[i + j + (m >> 1)]; 
        int t = (ll) v * w[dir ? n - n / m * j : n / m * j] % MOD;
        v = u - t < 0 ? u - t + MOD : u - t;
        u = u + t >= MOD ? u + t - MOD : u + t;
      }
    }
  } if (dir) for (int i = 0; i < n; ++i) a[i] = (ll) a[i] * inv_n % MOD;
}

int f_a[N];
ll fac[N], inv[N];

int main() {
  fac[0] = 1;
  for (int i = 1; i < N; ++i) fac[i] = i * fac[i - 1] % MOD;
  inv[N - 1] = bigMod(fac[N - 1], -1);
  for (int i = N - 1; i; --i) inv[i - 1] = i * inv[i] % MOD;
  int n, m;
  cin >> n >> m;
  int tot = 1;
  while (tot <= n * m) tot <<= 1; 
  prepare(tot);
  for (int i = 0; i <= m; ++i) f_a[i] = inv[m - i] * inv[m - i] % MOD * inv[i] % MOD;
  ntt(f_a, tot, 0);
  for (int i = 0; i < tot; ++i) f_a[i] = bigMod(f_a[i], n);
  ntt(f_a, tot, 1);
  ll ans = 0, mul = bigMod(fac[m] * fac[m] % MOD, n);
  for (int i = 0; i <= n * m; ++i) {
    ll add = mul * f_a[i] % MOD * fac[n * m - i] % MOD;
    (i & 1) ? (ans -= add) : (ans += add);
  }
  ans %= MOD, ans += MOD, ans %= MOD;
  cout << ans << '\n';
  return 0;
}