#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

constexpr int P = 1000000007;

ll powmod(ll n, ll k) {
    ll r = 1, t = n % P;
    for (; k != 0; k /= 2) {
        if (k & 1) r = r * t % P;
        t = t * t % P;
    }
    return r;
}
ll modinv(ll n) {
    return powmod(n, P - 2);
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, k;
    cin >> n >> k;

    vector<int> x(n);
    x[0] = 1;
    for (int i = 1; i < n; i++) {
        x[i] = (ll)x[i - 1] * modinv(i) % P * (k + i) % P;
    }

    ll r = 0;
    for (int i = 0; i < n; i++) {
        int a;
        cin >> a;

        r += (ll)a * x[i] % P * x[n - 1 - i] % P;
    }
    r %= P;

    cout << r << endl;

    return 0;
}