#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MN = 100100;
const ll M = 1e9+7;
inline ll mul(ll a, ll b) {return (a*b)%M;}
ll bp(ll b, ll p) {
ll ac = 1;
while(p) {
if(p&1) {ac = mul(ac,b);}
b = mul(b,b);
p >>= 1;
}
return ac;
}
inline ll inv(ll v) {return bp(v,M-2);}
ll fp[MN];
ll fac(ll n) {
if(n <= 1) {return 1;}
if(fp[n] != -1) {return fp[n];}
return fp[n] = mul(fac(n-1),n);
}
ll ch(ll n, ll k) {
if(k < 0 || k > n) {return 0;}
if(k <= 0 || k >= n) {return 1;}
return mul(mul(fac(n),inv(fac(k))),inv(fac(n-k)));
}
int main() {
memset(fp,-1,sizeof(fp));
ll n,k;
cin >> n >> k;
ll res = 0;
for(int i=0;i<k;i++) {
ll sgn = (i&1)?-1:1;
res += sgn*mul(bp(k-i,n),ch(n+1,i));
}
res = ((res%M)+M)%M;
cout << res << '\n';
}
