#define _USE_MATH_DEFINES
#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <string>
#include <vector>
#include <utility>
#include <complex>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <deque>
#include <tuple>
#include <bitset>
#include <limits>
#include <algorithm>
#include <random>
#include <complex>
#include <regex>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()	{cin.tie(0);	cout.sync_with_stdio(false);}
#define reach(i,a)	for(auto i:a)
#define rep(i,n)	for(int i=0;i<(int)n;i++)
#define REP(i,n)	for(int i=0;i<=(int)n;i++)
#define srep(i,a,n)	for(int i=a;i<(int)n;i++)
#define SREP(i,a,n)	for(int i=a;i<=(int)n;i++)
#define rrep(i,n)	for(int i=n-1;i>=0;i--)
#define RREP(i,n)	for(int i=n;i>=0;i--)
#define all(a)	(a).begin(),(a).end()
#define mp(a,b)	make_pair(a,b)
#define mt	make_tuple
#define pb	push_back
#define fst	first
#define scn second
int bitcnt(ll x) {
	x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
	x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
	x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
	x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
	x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
	x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
	return x;
}
int bitcnt(int x) {
	x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
	x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
	x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
	x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
	x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
	return x;
}
ll gcd(ll a, ll b) {
	return a%b == 0 ? b : gcd(b, a%b);
}
#define debug(x)	cout<<"case #" << x << ": " << endl
#define DEBUG 0
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ld eps = 1e-15;
const int dx[] = { 1,0,-1,0,0 };
const int dy[] = { 0,1,0,-1,0 };

// 1^x+2^x+...+n^x
ll dp[10010];
// xの逆元
ll inv[10010];
// x!
ll fac[10010];
// x!の逆元
ll invfac[10010];

ll modpow(ll x,ll m) {
	x %= mod;
	if (x) {
		ll ret = 1;
		while (m) {
			if (m & 1)	ret = (ret*x) % mod;
			x = (x*x) % mod;
			m >>= 1;
		}
		return ret;
	}
	return 0;
}

ll nCm(int n, int m) {
	return (fac[n] * ((invfac[n - m] * invfac[m]) % mod)) % mod;
}

int main() {
	ll n, k;	cin >> n >> k;
	inv[0] = inv[1] = fac[0] = fac[1] = invfac[0] = invfac[1] = 1;
	SREP(i, 2, k + 1) {
		inv[i] = modpow(i,mod-2);
		fac[i] = (i*fac[i - 1]) % mod;
		invfac[i] = (inv[i] * invfac[i - 1]) % mod;
	}
	dp[0] = n%mod;
	SREP(i, 1, k) {
		ll nxt = modpow(n, i + 1);
		rep(j, i) {
			nxt += mod + ((i + j + 1) & 1 ? -1 : 1)*((nCm(i + 1, j)*dp[j]) % mod);
			nxt %= mod;
		}
		dp[i] = (nxt*inv[i + 1]) % mod;
	}
	cout << dp[k] << endl;
	return 0;
}