#include<cstdio>
#include<iostream>
#define RI register int
#define CI const int&
using namespace std;
const int N=1<<21,mod=998244353;
int n,m,f[N],fact[N],ifac[N];
inline void inc(int& x,CI y)
{
    if ((x+=y)>=mod) x-=mod;
}
inline void dec(int& x,CI y)
{
    if ((x-=y)<0) x+=mod;
}
inline int quick_pow(int x,int p=mod-2,int mul=1)
{
    for (;p;p>>=1,x=1LL*x*x%mod) if (p&1) mul=1LL*mul*x%mod; return mul;
}
inline void init(CI n)
{
    fact[0]=1; for (RI i=1;i<=n;++i) fact[i]=1LL*fact[i-1]*i%mod;
    ifac[n]=quick_pow(fact[n]); for (RI i=n-1;i>=0;--i) ifac[i]=1LL*ifac[i+1]*(i+1)%mod;
}
inline int C(CI n,CI m)
{
    if (n<0||m<0||n<m) return 0;
    return 1LL*fact[n]*ifac[m]%mod*ifac[n-m]%mod;
}
namespace Poly
{
    int rev[N],lim,p;
    inline void init(CI n)
    {
        for (lim=1,p=0;lim<=n;lim<<=1,++p);
        for (RI i=0;i<lim;++i) rev[i]=(rev[i>>1]>>1)|((i&1)<<p-1);
    }
    inline void NTT(int *f,CI opt)
    {
        for (RI i=0;i<lim;++i) if (i<rev[i]) swap(f[i],f[rev[i]]);
        for (RI i=1;i<lim;i<<=1)
        {
            int m=i<<1,D=quick_pow(3,opt==1?(mod-1)/m:mod-1-(mod-1)/m);
            for (RI j=0;j<lim;j+=m)
            {
                int W=1; for (RI k=0;k<i;++k,W=1LL*W*D%mod)
                {
                    int x=f[j+k],y=1LL*f[i+j+k]*W%mod;
                    f[j+k]=f[i+j+k]=x; inc(f[j+k],y); dec(f[i+j+k],y);
                }
            }
        }
        if (!~opt)
        {
            int Inv=quick_pow(lim);
            for (RI i=0;i<lim;++i) f[i]=1LL*f[i]*Inv%mod;
        }
    }
}
int main()
{
    scanf("%d%d",&n,&m); init(n*m);
    for (RI i=0;i<=m;++i) f[i]=1LL*C(m,i)*C(m,i)%mod*fact[i]%mod;
    Poly::init(n*m); Poly::NTT(f,1);
    for (RI i=0;i<Poly::lim;++i) f[i]=quick_pow(f[i],n);
    Poly::NTT(f,-1); int ans=0;
    //for (RI i=0;i<=n*m;++i) printf("%d%c",f[i]," \n"[i==n*m]);
    for (RI i=0;i<=n*m;++i)
    {
        int tmp=1LL*f[i]*fact[n*m-i]%mod;
        if (i&1) dec(ans,tmp); else inc(ans,tmp);
    }
    return printf("%d",ans),0;
}