#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint1000000007;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001


int main(){
	
	int n;
	cin>>n;
	vector<int> x(n);
	int s = 0;
	rep(i,n){
		cin>>x[i];
		s += x[i];
	}
	mint ans = 0;
	if(s==1){
		cout<<1<<endl;
		return 0;
	}
	rep(i,n){
		mint p = 1;
		p *= x[i];
		p *= s-x[i];
		p /= s;
		p /= s-1;
		p *= s-1;
		ans += p;
	}
	ans ++;
	cout<<ans.val()<<endl;
	
	return 0;
}