#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll much(vector<int> x, ll sum) {
	if (x.size() == 2) {
		return x[0]*x[1];
	}
	ll ans = 0ll;
	if (x[0] < x[x.size()-1]) {
	  ll xxx = x[0];
	  ans = ((sum-xxx) * xxx);
	  x.erase(x.begin());
	  ans += much(x,xxx);
	}
	else {
	  ll xx = x[x.size()-1];
	  ans = (sum-xx * xx);
	  x.erase(x.begin()+x.size()-1);
		ans += much(x, sum-xx);
	}
	return ans;
}
int main() {
	int a;
	cin >> a;
	ll sum = 0ll;
	vector<int> v(a);
	for (int i = 0; i < a; i++) {
	  cin >> v[i]; 
	  sum += v[i];
	}
	ll ans = 0ll;
	cout << much(v, sum) << endl;
}