typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
const int MAX = 300000;
const int MOD = 1000000007;
 
 long long fac[MAX], finv[MAX], inv[MAX];
 
 // テーブルを作る前処理
 void COMinit() {
     fac[0] = fac[1] = 1;
     finv[0] = finv[1] = 1;
     inv[1] = 1;
     for (int i = 2; i < MAX; i++){
         fac[i] = fac[i - 1] * i % MOD;
         inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
         finv[i] = finv[i - 1] * inv[i] % MOD;
     }
 }
 
 // 二項係数計算
 long long COM(int n, int k){
     if (n < k) return 0;
     if (n < 0 || k < 0) return 0;
     return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
 }
int main() {
    COMinit();
    ll n,k;
    std::cin >> n>>k;
    vector<ll> a(n);
    
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }
    
    ll ans = 0;

    vector<ll> aite(n);
    aite[0] = 1;
    
    for (int i = 1; i < n; i++) {
        aite[i] = aite[i-1]*(k+i)%MOD*inv[i]%MOD;
        aite[i] %= MOD;
    }
    
    for (ll i = 0; i < n; i++) {
        ans += a[i]*aite[i]%MOD*aite[n-1-i]%MOD;
        ans %= MOD;
    }
    
    std::cout << ans << std::endl;
}