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

#define int long long
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define MOD 1000000007

int kk[200010];
int rkai[200010];
int a[200010];
int n, k;

int kai = 1;

int pow_mod(int n, int m){
	int ans = 1;
	while(m > 0){
		if(m & 1) ans = (ans * n) % MOD;
		n = (n * n) % MOD;
		m >>= 1;
	}
	return ans;
}
int ncr(int n, int r){
	return kk[n-k]* kai%MOD * rkai[n-r] % MOD;
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n >> k;

	for(int i = 0;i < n;i++){
		cin >> a[i];
	}

	int now = 1;
	rkai[0] = pow_mod(now, MOD-2);
	for(int i = 1;i <= n;i++){
		now =(now*i) % MOD;
		rkai[i] = pow_mod(now, MOD-2); 
	}

	for(int i = 1;i <= k;i++) kai = (kai*i) % MOD;
	kk[0] = kai;

	for(int i = 1;i <= n;i++){
		kk[i] = kk[i-1] * (k+i) % MOD; 
	}

	kai = pow_mod(kai, MOD-2);

	int ans = 0;
	for(int i = 0;i < n;i++){
		int l = i;
		int r = n-i-1; 
		ans += a[i] * ncr(k+l, k) % MOD * ncr(k+r, k) % MOD;
		ans %= MOD;
	}
	cout << ans << endl;
	return 0;
}