#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a[10005],ans = 0;
	bool flag = false;
	cin >> n;
	for (int i = 1;i <= n;i++){
		cin >> a[i];
	}
	for (int i = 1;i <= n;i++){
		for (int j = 1;j <= n;j++){
			for (int k = 1;k <= n;k++){
				if (a[i] == a[j] + a[k] && i != j && j != k && i != k){
					ans++;
					flag = true;
					break;
				} 
			}
			if (flag){
				break;
				flag = false;
			}
		}
	}
	cout << ans;
	return 0;
}