#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (int i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

ll pow_mod(ll x, ll n, ll mod){
    ll ret = 1;
    while(n > 0){
        if(n & 1) ret = (ret*x)%mod;
        x = x*x%mod;
        n >>=1;
    }
    return ret;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    ll n; cin >> n;
    vector<ll> x(n); rep(i, n) cin >> x[i];

    ll sum = 0;
    rep(i, n) sum += x[i];

    ll ans = 0;
    ll mul = 0;
    for(ll i=n-1; i>=0; i--){
        ans = ans + (x[i] * mul)%MOD;
        mul = (mul + x[i]) % MOD;
    }

    ans = ans*2 % MOD;

    ans = ans * pow_mod(sum, MOD-2, MOD) % MOD * pow_mod(sum-1, MOD-2, MOD) % MOD;
    ans = ans * (sum-1) % MOD;
    ans = (ans + 1)%MOD;
    cout << ans << endl;
}