#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <memory.h>
#include <math.h>
#include <assert.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <algorithm>
#include <string>
#include <functional>
#include <vector>
#include <deque>
#include <utility>
#include <bitset>
#include <limits.h>
#include <time.h>
using namespace std;
typedef long long ll;
typedef unsigned long long llu;
typedef double lf;
typedef unsigned int uint;
typedef long double llf;
typedef pair<int, int> pii;
int N;
ll res1;
int main() {
scanf("%d", &N);
ll sum = 0;
for(int i = 1; i <= N; i++) {
int si; scanf("%d", &si);
res1 += sum * si;
sum += si;
}
printf("%lld\n-bnjnfkafjnsdhbvsdfuhvbuigfuawefuawruewbwan\n", res1, sum);
return 0;
}
