#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 100010,mod = 1e9+7;
int qmi(int a,int k,int p){
int res = 1;
while(k){
if(k&1) res = res * a % p;
a = a * a %p;
k >>= 1;
}
return res;
}
int fact[N],infact[N];
int c(int n,int m){
if(n<0||m>n||m<0) return 0;
return fact[n] * infact[n-m]%mod * infact[m] % mod;
}
int s2(int n,int m){
int ans = 0;
for(int k=0;k<=m;k++){
if(k%2){
ans=(ans-c(m,k) % mod * qmi(m-k,n,mod) + mod)% mod;
}else{
ans=(ans + c(m,k) %mod * qmi(m-k,n,mod) )% mod;
}
}
return ans*infact[m]%mod;
}
signed main(){
int n,m;
cin>>n>>m;
fact[0]=1,infact[0]=1;
///就是这里,把n该成N就不对了为什么??
for(int i=1;i<=n;i++){
fact[i] = (fact[i-1]*i %mod);
infact[i]=(infact[i-1]*qmi(i,mod-2,mod))%mod;
}
int ans = s2(n,m);
cout<<ans<<'\n';
}