#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 = 200010;

ll inv[MAX];  // inv[i] : iの逆数のmod

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

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

    init();

    vl C(n);  // C[i] : Comb(k + i, k)
    C[0] = 1;
    exrep(i, 1, n-1) {
        C[i] = (k + i) * inv[i] % mod * C[i-1] % mod;
    }

    ll ans = 0;
    rep(i, n) {
        ll a;
        cin >> a;
        ans += a * C[i] % mod * C[n - 1 - i];
        ans %= mod;
    }

    out(ans);
    re0;
}