#include <bits/stdc++.h>

using namespace std;

long largestValue(vector <int> A ,int n) {
    // Return the largest value of any of A's nonempty subarrays.
    int i,j,mul=0;
    for(i=0;i<n;i++)
    {
        for(j=i+1;j<n;j++)
        {
            mul=(A[i]*A[j])+mul;
        }
    }
    return mul;
}

int main() {
    int n;
    cin >> n;
    vector<int> A(n);
    for(int A_i = 0; A_i < n; A_i++){
       cin >> A[A_i];
    }
    long result = largestValue(A,n);
    cout << result+5 << endl;
    return 0;
}