#include<iostream>
#include<iomanip>
#include<math.h>
#include<vector>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<bitset>
#include<random>
#include<time.h>
#define INF 1000000000ll
#define MOD 1000000007ll
#define EPS 1e-10
#define REP(i,m) for(long long i=0; i<m; i++)
#define FOR(i,n,m) for(long long i=n; i<m; i++)
#define DUMP(a) for(long long dump=0; dump<(ll)a.size(); dump++) { cout<<a[dump]; if(dump!=(ll)a.size()-1) cout<<" "; else cout<<endl; }
#define ALL(v) v.begin(),v.end()
#define pb push_back
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef long double ld;

ll _pow(ll a, ll n) {
	if(n==0) return 1;
	else {
		ll res = 1;
		ll buf = a;
		while(n>0) {
			if(n%2==1) {
				res *= buf;
				res %= MOD;
			}
			buf *= buf;
			buf %= MOD;
			n/=2;
		}
		return res;
	}
}

#define MAX_N 1000000
long long extgcd(long long a, long long b, long long& x, long long& y) {
	long long d = a;
	if (b != 0) {
		d = extgcd(b, a % b, y, x);
		y -= (a / b) * x;
	} else {
		x = 1; y = 0;
	}
	return d;
}
long long mod_inverse(long long a, long long m) {
	long long x, y;
	if(extgcd(a, m, x, y) == 1) return (m + x % m) % m;
	else return -1;
}
vector<long long> fact(MAX_N+1, INF);
long long mod_fact(long long n, long long& e) {
	if(fact[0] == INF) {
		fact[0]=1;
		if(MAX_N != 0) fact[1]=1;
		for(ll i = 2; i <= MAX_N; ++i) {
			fact[i] = (fact[i-1] * i) % MOD;
		}
	}
	e = 0;
	if(n == 0) return 1;
	long long res = mod_fact(n / MOD, e);
	e += n / MOD;
	if((n / MOD) % 2 != 0) return (res * (MOD - fact[n % MOD])) % MOD;
	return (res * fact[n % MOD]) % MOD;
}
// return nCk
long long mod_comb(long long n, long long k) {
	if(n < 0 || k < 0 || n < k) return 0;
	long long e1, e2, e3;
	long long a1 = mod_fact(n, e1), a2 = mod_fact(k, e2), a3 = mod_fact(n - k, e3);
	if(e1 > e2 + e3) return 0;
	return (a1 * mod_inverse((a2 * a3) % MOD, MOD)) % MOD;
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	ll n,k;
	cin>>n>>k;
	n%=MOD;
	vector<ld> ber(k+2,0);
	ber[0]=1;
	FOR(i,1,k+2) {
		REP(j,i) {
			if(j%2==i%2) ber[i]-=mod_comb(i+1,j)*ber[j];
			else ber[i]+=mod_comb(i+1,j)*ber[j];
		}
		ber[i]/=i+1;
	}
	ld ans=0;
	REP(i,k+2) {
		ans+=(_pow(n,(k+1)-i)*mod_comb(k+1,i))%MOD*ber[i];
		ans=round(ans);
	}
	ans-=ber[k+1];
	ll tmp=round(ans);
	tmp*=_pow(k+1,MOD-2);
	tmp=(tmp%MOD+MOD)%MOD;
	cout<<tmp<<endl;
}