/* -*- coding: utf-8 -*-
 *
 * 1102.cc:  No.1102 Remnants - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;
const int MOD = 1000000007;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N], cs[MAX_N];

/* subroutines */

int powmod(int a, int n) {  // a^n % MOD
  int pm = 1;
  while (n > 0) {
    if (n & 1) pm = (ll)pm * a % MOD;
    a = (ll)a * a % MOD;
    n >>= 1;
  }
  return pm;
}

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  for (int i = 0; i < n; i++) scanf("%d", as + i);

  cs[0] = 1;
  for (int i = 1; i < n; i++)
    cs[i] = (ll)cs[i - 1] * (k + i) % MOD * powmod(i, MOD - 2) % MOD;

  int sum = 0;
  for (int i = 0; i < n; i++) {
    int d = (ll)as[i] * cs[i] % MOD * cs[n - 1 - i] % MOD;
    sum = (sum + d) % MOD;
  }

  printf("%d\n", sum);
  return 0;
}