#include<bits/stdc++.h>
using namespace std;
const int N = 1048576;
const int mod = 998244353;
typedef long long LL;
constexpr LL fastpo(LL x, LL n, int mod) {
	LL res = 1;
	x %= mod;
	while(n) {
		if(n & 1) {
			res = res * x % mod;
		}
		x = x * x % mod;
		n /= 2;
	}
	
	return res;
}
constexpr LL G = fastpo(3, (mod - 1) / N, mod);
LL w[N];
LL A[N];
void NTT(LL p[], int n) {
	for (int i = 1, j = 0; i < n - 1; ++i) {
		for (int s = n; j ^= s >>= 1, ~j & s;);
		if (i < j) swap(p[i], p[j]);
	}
	for (int d = 0; (1 << d) < n; ++d) {
		int m = 1 << d, m2 = m * 2, rm = n >> (d + 1);
		for (int i = 0; i < n; i += m2) {
			for (int j = 0; j < m; ++j) {
				LL &p1 = p[i + j + m], &p2 = p[i + j];
				LL t = w[rm * j] * p1 % mod;
				p1 = p2 - t, p2 = p2 + t;
				if(p1 < 0) p1 += mod;
				if(p2 >= mod) p2 -= mod;
			} } }
}
LL fac[N], invfac[N];
LL c(int a, int b) {
	return fac[a] * invfac[a - b] % mod * invfac[b] % mod;
}
int main() {
	int n, m;
	scanf("%d%d", &n, &m);
	for(int i = 0; i < N; i++) {
		fac[i] = i == 0 ? 1 : fac[i - 1] * i % mod;
	}
	for(int i = 0; i < N; i++) {
		w[i] = i == 0 ? 1 : w[i - 1] * G % mod;
	}
	invfac[N - 1] = fastpo(fac[N - 1], mod - 2, mod);
	for(int i = N - 2; i >= 0; i--) {
		invfac[i] = invfac[i + 1] * (i + 1) % mod;
	}
	for(int i = 0; i <= m; i++) {
		A[i] = c(m, i) * fac[m] % mod * invfac[m - i] % mod;
		
	}
	NTT(A, N);
	for(int i = 0; i < N; i++) {
		A[i] = fastpo(A[i], n, mod);
	}
	NTT(A, N);
	reverse(A + 1, A + N);
	for(int i = 0; i < N; i++) {
		A[i] = A[i] * fastpo(N, mod - 2, mod) % mod;
	}
	LL ans = 0;
	for(int i = 0; i <= n * m; i++) {
		ans = (ans + (i % 2 == 0 ? 1 : -1) * A[i] * fac[n * m - i] % mod + mod) % mod;
	}
	cout << ans << endl;
}