为什么只有30分！！！

#include <iostream>
using namespace std;
const int N = 105;
int a[N];
int n, sum = 0;
int main() {
   cin >> n;
   for (int i = 1; i <= n; i++) cin >> a[i];
   for (int i = 1; i <= n - 1; i++) {
   	for (int j = i + 1; j <= n; j++) {
   		for (int k = 1; k <= n; k++) {
   			if (a[i] + a[j] == a[k]) sum++;
   		}
   	}
   }
   cout << sum;
   return 0;
}

谢谢！