#include <bits/stdc++.h>
#define rep(i,l,r) for(int i=l; i<=r; i++)
#define per(i,r,l) for(int i=r; i>=l; i--)
#define IOS {cin.tie(0);cout.tie(0);ios::sync_with_stdio(0);}
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
#define vi vector<int>
#define poly vi
const int N=1e6+6,mod=998244353,G=3;
ll qp(ll x,ll y){
    ll res=1;
    while(y){
        if(y&1)res=res*x%mod;
        x=x*x%mod; y>>=1;
    } return res;
}
const int Gi=qp(G,mod-2);
ll fac[N],inv[N];
ll C(int i,int j){
    return fac[i]*inv[j]%mod*inv[i-j]%mod;
}
ll A(int i,int j){
    return fac[i]*inv[i-j]%mod;
}
int limit=1,L=0; int r[N*4];
void NTT(poly& A,int type){
    A.resize(limit);
    for(int i=0;i<limit;++i)if(i<r[i])swap(A[i],A[r[i]]);
    for(int mid=1;mid<limit;mid<<=1){
        ll wn=qp(type==1 ? G:Gi, (mod-1)/(mid<<1));
        for(int j=0;j<limit;j+=(mid<<1)){
            ll w=1;
            for(int k=0;k<mid;k++,w=(w*wn)%mod){
                int x=A[j+k],y=w*A[j+k+mid]%mod;
                A[j+k]=(x+y)%mod, A[j+k+mid]=(x-y+mod)%mod;
            }
        }
    }
}
int main() {
    // IOS
    const int M=1e6;
    fac[0]=1; rep(i,1,M)fac[i]=fac[i-1]*i%mod;
    inv[M]=qp(fac[M],mod-2); per(i,M,1)inv[i-1]=inv[i]*i%mod;
    int n,m;cin>>n>>m;
    vi a(m+1);
    rep(i,0,m)a[i]=C(m,i)*A(m,i)%mod;
    // rep(i,0,m)cout<<a[i]<<' '; cout<<endl;
    limit=1,L=0;
    while(limit<=n*m+2)limit<<=1,++L;
    for(int i=0;i<limit;i++)r[i]=(r[i>>1]>>1|((i&1)<<(L-1)));
    NTT(a,1);
    rep(i,0,limit-1)a[i]=qp(a[i],n);
    NTT(a,-1);
    // cout<<"HHH"<<endl; 
    ll INV=qp(limit,mod-2);
    rep(i,0,limit-1)a[i]=a[i]*INV%mod;
    // rep(i,0,n*m)cout<<a[i]<<' '; cout<<'\n';
    ll ans=0,fl=1;
    rep(i,0,n*m){
        ans+=fl*fac[n*m-i]*a[i]%mod;
        fl=-fl;
    }
    cout<<(ans%mod+mod)%mod<<'\n';
    return 0;
}