#include<iostream>
using namespace std;
long mod=1e9+7;
long power(long a,long b){return b?power(a*a%mod,b/2)*(b%2?a:1)%mod:1;}
long N,M;
main()
{
	cin>>N>>M;
	long ans=0,C=1;
	for(int i=0;i<M;i++)
	{
		long now=power(M-i,N)*C%mod;
		if(i%2==0)(ans+=now)%=mod;
		else (ans+=mod-now)%=mod;
		C=C*(M-i)%mod*power(i+1,mod-2)%mod;
	}
	cout<<ans<<endl;
}