#include <bits/stdc++.h>
using namespace std;
int n , m;
const int N = 1 << 20;
const int mod = 998244353;
int re[N];
int w[2][N];
int qpow(int a,int b) {
    int ans = 1;
    while(b) {
        if(b & 1) ans = 1LL * ans * a  %mod;
        a = 1LL * a * a%mod; b>>=1;
    }
    return ans;
}
inline int getre(int n) {
    int len = 1 , bit = 0;
    while(len < n) {len <<= 1;bit++;}
    for(int i = 1;i < len;i++) re[i] = (re[i>>1]>>1)|((i&1)<<(bit-1));
    w[0][0] = w[1][0] = 1;
    w[0][1] = qpow(3 , (mod - 1) / len);
    w[1][1] = qpow(w[0][1] , mod - 2) ;
    for(int o=0;o < 2;o++) for(int i = 2;i < len;i++) {
        w[o][i] = 1LL * w[o][i - 1] * w[o][1] % mod;
    }
    return len;
}
inline void NTT(int *a,int n,int o=0) {
    for(int i = 1;i < n;i++) if(i < re[i]) swap(a[i] , a[re[i]]);
    int R;
    for(int k = 1;k < n;k <<= 1) 
        for(int i = 0,t=k<<1 , st = n/t ; i < n ; i+= t) {
            for(int j = 0, nw = 0 ;j < k ;j++ , nw += st) {
                R = 1LL * a[i + j + k] * w[o][nw] % mod;
                a[i + j + k] = (a[i + j] - R + mod) % mod;
                a[i + j] = (a[i + j] + R) % mod;
            }
        }
    if(o) {
        R = qpow(n , mod - 2);
        for(int i = 0;i < n;i++) a[i] = 1LL * a[i] * R % mod;
    }
}

int t[1000005] , rt[1005];
int C(int a,int b) {
    return 1LL * t[a] * rt[b] % mod * rt[a-b] % mod;
}
int A(int a,int b) {
    return 1LL * t[a] * rt[a - b] % mod;
}
int f[N];
int main() {
    ios::sync_with_stdio(false) ; cin.tie(0) ;
    cin >> n >> m;
    t[0] = rt[0] = 1;
    for(int i = 1;i <= m * n;i++) {
        t[i] = 1LL * t[i - 1] * i % mod;
        if(i <= m) rt[i] = qpow(t[i] , mod - 2);
    }
    int len = getre(n * m + 1) ;
    for(int i = 0;i <= m;i++) {
        f[i] = 1LL * C(m , i) * A(m , i) % mod;
        if(i & 1) f[i] = (mod - f[i]) %mod;
        // printf("%d %d\n",i,f[i]) ;
    }
    // printf("L %d\n",len) ;
    NTT(f , len , 0) ;
    for(int i = 0;i < len;i++) f[i] = qpow(f[i] , n) ;
    NTT(f , len , 1);
    int ans = 0;
    for(int i = 0;i <= n*m;i++) {
        ans = (ans + 1LL * f[i] * t[n*m - i]) %  mod;
        // printf("%d %d\n",i,f[i]) ;
    }
    cout << ans;
    return 0;
}