#include <stdio.h>

const long long mod = 1000000007;
long long N,f[100100],fact[100100]; int K;

long long fpow(long long a, long long p)
{
	long long r = 1;
	while (p){
		if (p & 1) r = r * a % mod;
		a = a * a % mod;
		p /= 2;
	}
	return r;
}

long long inv(long long a)
{
	return fpow(a, mod-2);
}

long long proc()
{
	scanf ("%lld %d",&N,&K);
	N %= mod;
	for (int i=1;i<=K+1;i++) f[i] = (f[i-1] + fpow(i,K)) % mod;

	if (N <= K+1) return f[N];

	long long ans = 0;
	for (int i=1;i<=K+1;i++){
		long long r = f[i] * inv(fact[i] * fact[K+1-i] % mod * (N - i) % mod) % mod;
		if (i % 2 == K % 2) r = mod - r;
		ans = (ans + r) % mod;
	}
	for (int i=0;i<=K+1;i++) ans = ans * (N - i) % mod;

	return ans;
}

int main()
{
	fact[0] = 1;
	for (int i=1;i<100100;i++) fact[i] = fact[i-1] * i % mod;

	printf ("%lld\n",proc());

	return 0;
}