#include <iostream>
using namespace std;
#include <atcoder/modint>

int main() {
    cin.tie(nullptr), ios::sync_with_stdio(false);
    long long ret = 0, len = 0, N, x;
    cin >> N;
    while (N--) cin >> x, len += x, ret += x * (x - 1);
    cout << (len - atcoder::modint1000000007(ret) / len).val() << '\n';
}