#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const ll MOD=1e9+7;
ll powmod(ll a, ll k){
    ll ap=a, ans=1;
    while(k){
        if(k&1){
            ans*=ap;
            ans%=MOD;
        }
        ap=ap*ap;
        ap%=MOD;
        k>>=1;
    }
    return ans;
}
ll inv(ll a){
    return powmod(a, MOD-2);
}
int main()
{
	int n, k; cin>>n>>k;
    ll a[200020];
    for(int i=0; i<n; i++) cin>>a[i];
    ll c[200020];
    c[0]=1;
    for(int i=1; i<=n; i++){
        c[i]=c[i-1]*(k+i)%MOD*inv(i)%MOD;
    }
    ll ans=0;
    for(int i=0; i<n; i++){
        (ans+=a[i]*c[i]%MOD*c[n-i-1])%=MOD;
    }
    cout<<ans<<endl;
	return 0;
}