#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;
	}
}

ll A[10010];
ll N,K;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	cin>>N>>K;
	N%=MOD;
	ll sum=0;
	A[0]=0;
	FOR(i,1,K+2) {
		sum+=_pow(i,K);
		sum%=MOD;
		A[i]=sum;
	}
	if(N<=K+1) {
		cout<<A[N]<<endl;
		return 0;
	}
	ll ans=0;
	ll num=1;
	ll den=1;
	REP(i,K+2) {
		num*=N-i;
		num%=MOD;
	}
	REP(i,K+1) {
		den*=-(i+1);
		den%=MOD;
	}
	REP(i,K+2) {
		ll plus=(A[i]*num)%MOD;
		plus*=_pow(N-i,MOD-2);
		plus%=MOD;
		if(i) {
			den*=_pow(-(K+2-i),MOD-2);
			den%=MOD;
			den*=i;
			den%=MOD;
		}
		plus*=_pow(den,MOD-2);
		plus%=MOD;
		ans+=plus;
		ans%=MOD;
	}
	cout<<(ans%MOD+MOD)%MOD<<endl;
}