# include <bits/stdc++.h>
using namespace std;
const int mod=1e9+7;
typedef long long ll;
ll fac[100010],inv[100010];
ll C(int n,int m){return fac[n]*inv[n-m]%mod*inv[m]%mod;}
ll power(ll a,int b)
{
	ll ans=1;
	for(;b;b>>=1,a=a*a%mod)
		if(b&1) ans=ans*a%mod;
	return ans;
}
int calc(int n,int m)
{
	int ans=0;
	for(int i=0;i<m;i++) ans=(ans+(i&1?mod-C(n,i):C(n,i))*power(m-i,n))%mod;
	return ans;
}
int main()
{
	int n,m;
	cin>>n>>m;
	fac[0]=fac[1]=inv[0]=inv[1]=1;
	for(int i=2;i<=n;i++) fac[i]=fac[i-1]*i%mod;
	for(int i=2;i<=n;i++) inv[i]=(mod-mod/i)*inv[mod%i]%mod;
	for(int i=2;i<=n;i++) inv[i]=inv[i-1]*inv[i]%mod;
	cout<<(calc(n,m)-calc(n,m-1)+mod)%mod<<endl;
	return 0;
}