#include<bits/stdc++.h>
using namespace std;
int a[110];
int main() {
	int n;
	cin >> n;
	for (int i=1;i<=n;i++) {
		cin >> a[i];
	}
	sort(a+1,a+n+1);
	int s = 0;
	for (int i=1;i<=n;i++) {
		if (a[i] == s) {
			a[i] = 0;
		} else {
			s = a[i];
		}
	}
	int c = 0;
	for (int i=1;i<n;i++) {
		if (a[i] == 0) {
			continue;
		}
		for (int j=i+1;j<=n;j++) {
			if (a[j] == 0) {
				continue;
			}
			for (int k=1;k<=n;k++) {
				if (a[k] == 0) {
					continue;
				}
				if (k == i || k == j) {
					continue;
				}
				if (a[i]+a[j] == a[k]) {
					c++;
				}
			}
		}
	}
	cout << c;
}