#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef long long ll;
const ll MOD = 1000000007;

ll N, K;
ll A[200000];
ll cum_sum[200001];

ll inv(ll n){
    if(n == 1) return 1;
    else return MOD-inv(MOD%n)*(MOD/n)%MOD;
}

ll cnt[200005];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    cin >> N >> K;
    for(int i = 0; i < N; i++) cin >> A[i];
    for(int i = 0; i < N; i++) cum_sum[i+1] = cum_sum[i]+A[i];
    ll ans = 0;
    cnt[1] = 1;
    for(int i = 2; i <= N; i++){
        cnt[i] = (((cnt[i-1]*(K+i-1))%MOD)*inv(i-1))%MOD;
    }
    for(int i = 1; i <= N; i++){
        ll c = (cnt[i]*cnt[N-i+1])%MOD;
        ans += (A[i-1]*c)%MOD;
        ans %= MOD;
    }
    cout << ans << endl;
}