Particle Accelerator II

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
	int n;
	cin >> n;
	ll p;
	ll t = 0;
	cin >> p;
	for (int i=1; i<n; i++) {
		ll b;
		cin >> b;
		t += b*p;
		p += b;
	}
	cout << t;

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED