#include<bits/stdc++.h>
using namespace std;
#define rep(i,x,y) for (int i=(x);i<=(y);i++)
#define drep(i,y,x) for (int i=(y);i>=(x);i--)
#define pii pair<int,int>
#define fir first
#define sec second
#define MP make_pair
#define templ template<typename T>
templ bool chkmin(T &x,T y){return x>y?x=y,1:0;}
templ bool chkmax(T &x,T y){return x<y?x=y,1:0;}
void file() {
    #ifdef zqj
    freopen("a.in","r",stdin);
    #endif
}
typedef long long ll;
#define sz (1<<21)
const ll mod=998244353;

int rev[sz],wn[sz];
int lim, invlim; 
ll ksm(ll a,ll b,ll ans=1) {
    for (;b;b>>=1,a=a*a%mod) if (b&1) ans=ans*a%mod;
    return ans;
}
void init(int len) {
    lim = 2 << __lg(len-1);
    invlim = mod - (mod - 1) / lim;
    for (static int i = 1; i < lim; i += i) {
        wn[i] = 1;
        const int w = ksm(3,mod/i/2);
        for (int j = 1; j < i; j ++) {
            wn[i+j] = 1ll*wn[i+j-1]*w%mod;
        }
    }
    for (int i = 1; i < lim; ++i) {
        rev[i] = rev[i >> 1] >> 1 | (i % 2u * lim / 2);
    }
}
void DFT(int *a) {
    static unsigned long long t[sz];
    for (int i = 0; i < lim; i++) {
        t[i]=a[rev[i]];
    }
    for (int i = 1; i < lim; i += i) {
        for (int j = 0; j < lim; j += i + i) {
            for (int k=0;k<i;++k) {
                const unsigned long long x=t[i+j+k]*wn[i+k]%mod;
                t[i+j+k]=t[k+j]+mod-x,t[k+j]+=x;
            }
        }
    }
    for (int i = 0; i < lim; i++) a[i] = t[i] % mod;
}
void IDFT(int *a) {
    DFT(a); reverse(a+1,a+lim);
    for (int i = 0; i < lim; i++) a[i]= 1ll * a[i] * invlim % mod;
}

int n,m;

ll C[1010][1010];
ll fac[sz];

int main() {
    file();
    ios::sync_with_stdio(false),cin.tie(0);
    cin>>n>>m;
    rep(i,0,m) C[i][0]=1;
    rep(i,1,m) rep(j,1,i) (C[i][j]=C[i-1][j]+C[i-1][j-1])%=mod;
    fac[0]=1; rep(i,1,n*m) fac[i]=fac[i-1]*i%mod;
    static int a[sz];
    rep(i,0,m) a[i]=C[m][i]*C[m][i]%mod*fac[i]%mod;
    init(n*m+1);
    DFT(a);
    rep(i,0,lim-1) a[i]=ksm(a[i],n);
    IDFT(a);
    ll ans=0;
    rep(i,0,n*m) (ans+=a[i]*fac[n*m-i]%mod*((i&1)?mod-1:1)%mod)%=mod;
    cout<<ans;
    return 0;
}