#include <bits/stdc++.h>
using namespace std;
 
#define fi first
#define se second
#define pb push_back
using vi = vector <int>;
using ll = long long;
using pii = pair <int, int>;
//~ const ll mod = 998244353;
const ll mod = 1e9 + 7;
ll qpow(ll a, ll b, ll m = mod) { ll r = 1, t = a;
	for(; b; b /= 2) { if(b & 1) r = r * t % m; t = t * t % m; } return r; }

const int N = 2e5 + 11;
ll inv[N];

int a[N];

ll f[N];
// f[i] = binom(i + k - 1, i - 1)

int main() {
	inv[1] = 1;
	for(int i = 2; i < N; i ++)
		inv[i] = (mod - mod / i) * inv[mod % i] % mod;
	
	ios :: sync_with_stdio(false);
	
	int n, k; cin >> n >> k;
	for(int i = 1; i <= n; i ++)
		cin >> a[i];
	
	f[1] = 1;
	for(int i = 2; i <= n; i ++)
		f[i] = f[i - 1] * (i + k - 1) % mod * inv[i - 1] % mod;
	
	ll ans = 0;
	for(int i = 1; i <= n; i ++) {
		ans += a[i] * f[i] % mod * f[n - i + 1] % mod;
		ans %= mod;
	}
	
	if(ans < 0) ans += mod;
	cout << ans << '\n';
}