#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=long long;
using ld=long double;
ld pie=3.14159265359;
ll inf=10000000000000001;
ll mod=1000000007;
ll modpow(ll x, ll n) {
  x = x%mod;
  if(n==0) return 1;  //再帰の終了条件

  else if(n%2==1) {
    return (x*modpow(x, n-1))%mod;  //nが奇数ならnを1ずらす
  }
  else return modpow((x*x)%mod, n/2)%mod;  //nが偶数ならnが半分になる
}
int main(){
	ll n,k;
	cin >> n >> k;
	ll ans=modpow(n,k+1);
	ans+=mod-(modpow(n-1,k)*n)%mod;
	ans%=mod;
	cout << ans << endl;
}