#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <utility>
#include <cmath>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <numeric>
#include <functional>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define exrep(i, a, b) for(ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll mod = 1000000007;
const ll INF = 1e16;

const ll MAX = 20010;

ll fact[MAX];  // fact[i] : iの階乗のmod
ll inv[MAX];  // inv[i] : iの逆数のmod
ll invfact[MAX];  // invfact[i] : iの階乗の逆数のmod

void init() {
    fact[0] = 1;
    inv[0] = inv[1] = 1;
    invfact[0] = 1;
    for(ll i = 1; i < MAX; i++) {
        fact[i] = i * fact[i-1] % mod;
        if(i >= 2) {
            inv[i] = mod - inv[mod % i] * (mod / i) % mod;
        }
        invfact[i] = invfact[i-1] * inv[i] % mod;
    }
}

// nCrをO(n)で求める。 
ll Comb(ll n, ll r) {
    if(r < 0 || n < 0 || n < r) {
        return 0;
    }
    ll res = fact[n];
    res = (res * invfact[r]) % mod;
    res = (res * invfact[n - r]) % mod;
    return res;
}

int main() {
    ll n, k;
    cin >> n >> k;

    init();

    vl B(k+1);  // B[i] : i番目のベルヌーイ数
    B[0] = 1;
    exrep(i, 1, k) {
        rep(j, i) {
            B[i] += Comb(i+1, j) * B[j];
            B[i] %= mod;
        }
        B[i] = B[i] * (mod - inv[i+1]) % mod;
    }

    vl vec(k+2);  // vec[i] : n^i
    vec[0] = 1;
    exrep(i, 1, k+1) {
        vec[i] = vec[i-1] * (n % mod) % mod;
    }

    ll S_k = 0;  // Σ i^k (1 <= i <= n)
    exrep(i, 0, k) {
        S_k += Comb(k+1, i) * B[i] % mod * vec[k + 1 - i];
        S_k %= mod;
    }

    S_k = S_k * inv[k+1] % mod;
    
    out(S_k);
    re0;
}