#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(ll i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
constexpr ll MOD=1000000007;
constexpr ll INF=2e18;

ll power(ll x, ll y){
    x%=MOD;
    ll ret=1;
    while(y){
        if(y&1) ret=ret*x%MOD;
        x=x*x%MOD;
        y>>=1;
    }
    return ret;
}
ll divid(ll x, ll y){
    x%=MOD;
    return x*power(y,MOD-2)%MOD;
}

int main(){
    ll n, k; cin >> n >> k;
    ll p=divid(n-1,n);
    ll q=power(n,k);
    cout << divid(q*(1-power(p,k)+MOD),1-p+MOD) << endl;
}