#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; ++i)
#define all(a) (a).begin(), (a).end()

int main() {
    cin.tie(nullptr);
    
    int N;
    cin >> N;
    
    vector<ll> cnt(9, 0);
    rep(i, 0, N) {
        int A;
        cin >> A;
        cnt[A]++;
    }
    
    ll ans = 0;
    rep(ii, 1, 9) {
        ll i = (ll)ii;
        ll fac = i;
        rep(j, 1, 9) {
            ans += fac * cnt[j] * cnt[i];
            fac *= i;
        }
    }
    
    cout << ans << '\n';
}