#include<bits/stdc++.h>
using namespace std;
#define For(i,a,b) for(int i=(a);i<=(b);i++)
#define Rof(i,a,b) for(int i=(a);i>=(b);i--)
#define wln putchar('\n')
const int N=1005,M=1000005,MOD=998244353,N2=1<<20,G=3;
int sqr(int x){return 1ll*x*x%MOD;}
int mo(int x){return x>=MOD?x-MOD:x;}
void moplus(int &x,int y){x=mo(x+y);}
int ksm(int a,int b)
{
    int res=1;
    while(b)
    {
        if(b&1)res=1ll*res*a%MOD;
        a=1ll*a*a%MOD;
        b>>=1;
    }
    return res;
}
int fac[M],ifac[M];
void math_init(int n)
{
    fac[0]=1;
    For(i,1,n)fac[i]=1ll*fac[i-1]*i%MOD;
    ifac[n]=ksm(fac[n],MOD-2);
    Rof(i,n,1)ifac[i-1]=1ll*ifac[i]*i%MOD;
}
int getC(int a,int b){return 1ll*fac[a]*ifac[b]%MOD*ifac[a-b]%MOD;}
void dft(int n,int a[],int w[])
{
    for(int i=0;(1<<i)<n;i++)
        for(int j=0;j<n;j+=1<<i+1)
            For(k,0,(1<<i)-1)
            {
                int x=a[j+k],y=1ll*w[(n>>i+1)*k]*a[j+(1<<i)+k]%MOD;
                a[j+k]=mo(x+y); a[j+(1<<i)+k]=mo(x-y+MOD);
            }
}
void mul(int n,int a[],int b[])
{
    static int r[N2],w[N2>>1];
    int invn=ksm(n,MOD-2);
    r[0]=0;
    For(i,1,n-1)
    {
        r[i]=r[i>>1]>>1|(i&1)*(n>>1);
        if(r[i]<i)swap(a[r[i]],a[i]),swap(b[r[i]],b[i]);
    }
    w[0]=1; w[1]=ksm(G,(MOD-1)/n);
    For(i,2,(n>>1)-1)w[i]=1ll*w[i-1]*w[1]%MOD;
    dft(n,a,w); dft(n,b,w);
    For(i,0,n-1)
    {
        a[i]=1ll*a[i]*b[i]%MOD;
        if(r[i]<i)swap(a[r[i]],a[i]);
    }
    dft(n,a,w);
    reverse(a+1,a+n);
    For(i,0,n-1)a[i]=1ll*a[i]*invn%MOD;
}
void mul(int &lena,int a[],int lenb,int b[])
{
    int n=1;
    while(n<lena+lenb-1)n<<=1;
    fill(a+lena,a+n,0);
    fill(b+lenb,b+n,0);
    mul(n,a,b);
    while(n&&a[n-1]==0)n--;
    lena=n;
}
int n,m,a[N2],lena,b[N2],lenb,c[N2];
int main()
{
    scanf("%d%d",&n,&m);
    math_init(n*m);
    For(i,0,m)a[i]=1ll*sqr(getC(m,i))*fac[i]%MOD;
    lena=m+1; lenb=1;
    b[0]=1;
    int x=n;
    while(x)
    {
        if(x&1)
        {
            copy(a,a+lena,c);
            mul(lenb,b,lena,c);
        }
        copy(a,a+lena,c);
        mul(lena,a,lena,c);
        x>>=1;
        // printf("a:");
        // For(i,0,lena-1)printf("%d ",a[i]); wln;
        // printf("b:");
        // For(i,0,lenb-1)printf("%d ",b[i]); wln;
    }
    //printf("qwq\n");
    int res=0;
    For(i,0,n*m)
    {
        int s=1ll*b[i]*fac[n*m-i]%MOD;
        if(i&1)moplus(res,MOD-s);
        else moplus(res,s);
    }
    printf("%d",res);
}