#include <bits/stdc++.h>
using namespace std;
 
int lagrange_interpolating_polynomial(vector<int64_t> xs, vector<int64_t> ys, int64_t x, int MOD) {
    auto mod = [&](auto n) { return (n % MOD + MOD) % MOD; };
    transform(begin(xs), end(xs), begin(xs), mod);
    transform(begin(ys), end(ys), begin(ys), mod);
    x = mod(x);
    int n = size(xs);
    vector<int64_t> inv(n + 1, 1), L(n + 1, 1), R(n + 1, 1);
    for (int i = 1; i <= n; ++i) {
        if (i > 1) inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        L[i] = L[i - 1] * ((x + MOD - xs[i - 1]) % MOD) % MOD * inv[i] % MOD;
        R[i] = R[i - 1] * ((x + MOD - xs[n - i]) % MOD) % MOD * inv[i] % MOD;
    }
    int ans = 0;
    for (int i = 0; i < n; ++i) {
        auto P = ((n - i - 1) & 1 ? MOD - 1 : 1) * (L[i] * R[n - i - 1] % MOD) % MOD;
        ans = (ans + ys[i] * P % MOD) % MOD;
    }
    return ans;
}
 
int64_t mod_pow(int64_t x, int64_t n, int MOD) {
    int64_t res = 1;
    while (n > 0) {
        if (n & 1) (res *= x) %= MOD;
        (x *= x) %= MOD;
        n >>= 1;
    }
    return res;
}
 
int faulhaber_formula(int64_t n, int k, int MOD) {
    vector<int64_t> xs(k + 2), ys(k + 2);
    for (int i = 0; i < k + 2; ++i) {
        xs[i] = (i + 1) % MOD;
        ys[i] = mod_pow(i + 1, k, MOD);
        if (i) (ys[i] += ys[i - 1]) %= MOD;
    }
    return lagrange_interpolating_polynomial(xs, ys, n, MOD);
}
 
int main() {
    long n, k;
    cin >> n >> k;
    const int MOD = 1'000'000'007;
    cout << faulhaber_formula(n, k, MOD) << endl;
    return 0;
}