#include<bits/stdc++.h>
using namespace std;
const int N = 105 + 5;
int n, a[N], t, ans;
int main() {
	cin >> n;
	for(int i = 1; i <= n; i++){
		cin >> a[i];
	}
	for(int i = 1; i <= n; i++){
		int f = 0;
		for(int j = i; j <= n; j++){
			for(int k = i + 1; k <= n; k++){
				if(a[i] + a[j] == a[k]){
					f = 1;
				}
			}
		}
		ans += f;
	}
	cout << ans;
	return 0;
}