#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using namespace atcoder;

#define ll long long

using mint = modint1000000007;

void solve()
{
    int n, k; cin >> n >> k;
    vector<int> a(n);
    for(int i=0; i<n; ++i) cin >> a[i];

    if (k==0)
    {
        mint answer = 0;
        for (auto &x: a) answer += x;
        cout << answer.val() << "\n";
        return;
    }

    vector<mint> fact(n+1);
    fact[0] = mint(1);
    for (int i=0; i<n; ++i) fact[i+1] = fact[i] * (i+1);

    vector<mint> inv(n+1);
    inv[n] = fact[n].inv();
    for (int i=n; i>0; --i) inv[i-1] = inv[i] * i;

    vector<mint> fk(n+1);
    fk[0] = mint(1);
    for (int i=1; i<=n; ++i) fk[i] = fk[i-1] * (k + i);

    auto comb = [&](int i) { return fk[i] * inv[i]; };
    mint answer = mint(0);
    for(int i=0; i<n; ++i)
    {
        answer += a[i] * comb(i) * comb(n - i - 1);
    }
    cout << answer.val() << "\n";
}


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

    int t = 1;
    // std::cin >> t;
    while (t--)
        solve();

    return 0;
}