#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define rep(a,b,c) for(ll a=b;a<c;a++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

void get(vll &a){re(i,a.size()) scanf("%lld",&a[i]);}
void get(vvl &a){re(i,a.size()) re(j,a[0].size()) scanf("%lld",&a[i][j]);}
void print(vll &a){re(i,a.size()) cout<<a[i]<<(i==a.size()-1?"\n":" ");}
void print(vvl &a){re(i,a.size()) re(j,a[0].size())cout<<a[i][j]<<(j==a[0].size()-1?"\n":" ");}

#define P 1000000007
#define N_MAX 1000000
vector<ll> fac(N_MAX+1);
vector<ll> finv(N_MAX+1);
vector<ll> inv(N_MAX+1);

ll comb(ll n, ll k){
  if(n<0||k<0||n<k) return 0;
  return (((fac[n]*finv[n-k])%P)*finv[k])%P;
}
ll perm(ll n, ll k){
  if(n<0||k<0||n<k) return 0;
  return (fac[n]*finv[n-k])%P;
}
void init(){
  fac[0] = finv[0] = fac[1] = finv[1] = inv[1] = 1;
  for(int i = 2; i <= N_MAX; i++){
    fac[i] = (fac[i-1]*i)%P;
    inv[i] = ((-(P/i)*inv[P%i])%P+P)%P;
    finv[i] = (finv[i-1]*inv[i])%P;
  }
}
ll pp(ll a, ll b){ return (a * b)%P;}
ll mpow(ll a, ll b, ll p = -1){
  ll ret = 1, num = a;
  if(p==-1){
    while(b>0){
      if(b%2) ret *= num;
      num = num * num;
      b /= 2;
    }
  }else{
    while(b>0){
      if(b%2) ret = (ret*num)%p;
      num = (num*num)%p;
      b /= 2;
    }
  }
  return ret;
}
int main() {
  init();
  ll n, k;std::cin >> n >> k;

  vll a(n);get(a);
  ll ans = 0;
  vll lc(n, 0), rc(n, 0);
  lc[0] = 1;
  rc[n-1] = 1;
  for(ll i=1;i<n;i++){
    ll pre = lc[i-1];
    pre = pp(pre, i+k);
    pre = pp(pre, inv[i]);
    lc[i] = pre;
  }
  for(int i=n-2;i>=0;i--){
    ll pre = rc[i+1];
    pre = pp(pre, n-1-i + k);
    pre = pp(pre, inv[n-1-i]);
    rc[i] = pre;
  }

  for(int i=0;i<n;i++) {
    ans = (ans + ((a[i] * pp(lc[i], rc[i]))%P))%P;
  }
  std::cout << ans << '\n';
}