#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const ll MOD = 1000000007;

ll dp[10005], f[10005], fi[10005];

ll modpow(ll x, ll n) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % MOD;
        x = x * x % MOD;
        n >>= 1;
    }
    return res;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n;
    int k;
    cin >> n >> k;
    f[0] = 1;
    for (int i = 1; i <= k + 1; i++) f[i] = f[i - 1] * i % MOD;
    fi[k + 1] = modpow(f[k + 1], MOD - 2);
    for (int i = k + 1; i > 0; i--) fi[i - 1] = fi[i] * i % MOD;
    auto comb = [&](int r, int c) {
        return f[r] * fi[c] % MOD * fi[r - c] % MOD;
    };
    dp[0] = n % MOD;
    for (int i = 1; i <= k; i++) {
        dp[i] = (modpow((n + 1) % MOD, i + 1) + MOD - 1) % MOD;
        for (int j = 0; j < i; j++) {
            (dp[i] += MOD - dp[j] * comb(i + 1, j) % MOD) %= MOD;
        }
        (dp[i] *= modpow(i + 1, MOD - 2)) %= MOD;
    }
    cout << dp[k] << endl;
    return 0;
}