#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
long long modpow(long long a, long long b){
  long long ans = 1;
  while (b > 0){
    if (b % 2 == 1){
      ans *= a;
      ans %= MOD;
    }
    a *= a;
    a %= MOD;
    b /= 2;
  }
  return ans;
}
long long modinv(long long a){
  return modpow(a, MOD - 2);
}
int main(){
  int N;
  cin >> N;
  vector<int> x(N);
  for (int i = 0; i < N; i++){
    cin >> x[i];
  }
  int S = 0;
  for (int i = 0; i < N; i++){
    S += x[i];
  }
  long long all = (long long) S * (S - 1) / 2;
  long long same = 0;
  for (int i = 0; i < N; i++){
    same += (long long) x[i] * (x[i] - 1) / 2;
  }
  long long p = (same % MOD) * modinv(all % MOD) % MOD;
  long long q = MOD + 1 - p;
  cout << ((S - 1) * q + 1) % MOD << endl;
}