#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <map>
#include <queue>
#include <deque>
#include <string>
#include <stack>
#include <vector>
#include <set>
#include <tuple>
#include <utility>
#include <functional>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef tuple<int,int,int> T;
const int INF = 1000000000;
const int MOD = 1000000007;

template <class T, class U>
//p-2乗が逆元
T pow_mod(T a,T b,U m){
	if(b == 0)return 1;
	else if(b % 2 == 0){
		ll t = pow_mod(a,b/2,m);
		return t * t % m;
	}
	return a  * pow_mod(a,b-1,m) % m;
}

int main(){
	ll n,k;
	cin >> n >> k;
	ll ans = 0;
	vector<ll> a(n);
	for(ll i = 0;i < n;i++)cin >> a[i];

	vector<ll> comb(n);
	comb[0] = 1;
	for(ll i = 1;i < n;i++){
		comb[i] = (comb[i-1] * (k+i) % MOD) * pow_mod(i,(ll)MOD-2,MOD) % MOD;
	}

	for(ll i = 0;i < n;i++){
		ans += (comb[i] * a[i]) % MOD * comb[n-1-i];
		ans %= MOD;
	}
	
	cout << ans << endl;
}