#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define M 1000000007
ll n,m,ans,k[100005],r[100005];
ll pw(ll a,ll b){
	ll res=1;
	while(b){
		if(b&1)res=res*a%M;
		b>>=1;
		a=a*a%M;
	}
	return res;
}
ll cm(ll a,ll b){
	return k[a]*r[b]%M*r[a-b]%M;
}
int main(void){
    cin>>n>>m;
    k[0]=1,r[0]=1;
    for(ll i=1;i<=m;i++){
		k[i]=k[i-1]*i%M;
		r[i]=pw(k[i],M-2);
	}
	ans=pw(m,n);
	for(ll i=1;i<=m;i++){
		if(i%2)ans=(ans+M-cm(m,i)*pw(m-i,n)%M)%M;
		else ans=(ans+cm(m,i)*pw(m-i,n)%M)%M;
	}
	cout<<ans<<endl;
}