#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

int cnt[9];
ll ans;

int main() {
  int n; cin >> n;
  for (int i = 0; i < n; i++) {
    int a; cin >> a;
    cnt[a]++;
  }
  for (int k = 1; k <= 8; k++) {
    for (int l = 1; l <= 8; l++) {
      ans += (ll)cnt[k] * cnt[l] * pow(k, l);
    }
  }
  cout << ans << endl;
  return 0;
}