#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

#include <atcoder/all>
using namespace atcoder;

#define REP(i, n) for(int i = 0; i < (int)n; i++)
#define LREP(i, n) for(LL i = 0; i < (LL)n; i++)
#define RREP(i, n) for(int i = (int)n-1; i >= 0; i--)
#define V(T) vector<T>

#define P pair<int, int>
#define LP pair<LL, LL>
#define T3 tuple<LL, LL, LL>
#define T4 tuple<LL, LL, LL, LL>
#define INF 1000000007
#define SIZE 500100
#define MOD 1000000007
typedef long long LL;

LL N, K;
LL A[SIZE], C[SIZE];

int main() {
	cin >> N >> K;
	REP(i, N) cin >> A[i];

	LREP(i, N) {
		if (i == 0) {
			C[i] = 1;
		}
		else {
			C[i] = (C[i - 1] * (K + i)) % MOD;
			C[i] = (C[i] * inv_mod(i, MOD)) % MOD;
		}
	}

	LL ans = 0;
	REP(i, N) {
		LL c = A[i];
		c = (c * C[i]) % MOD;
		c = (c * C[N - 1 - i]) % MOD;
		ans = (ans + c) % MOD;
	}
	cout << ans << endl;
}