#include<stdio.h>
int main() {
	int n;
	scanf_s("%d", &n);
	int a[101];
	int x = 0;
	for (int i = 0; i < n; i++) {
		scanf_s("%d", &a[i]);
	}
	for (int i = 0; i < n; i++) {
		for (int j = i+1; j < n; j++) {
			for (int k = j+1; k < n; k++) {
				if (i != j && i != k && j != k) {
					if (a[i] + a[j] == a[k]) {
						x++;
					}
				}
			}
		}
	}
	printf("%d", x);
	return 0;
}