int n, i, x, y; scanf("%d", &n); int num[n]; for (i = 0; i < n; i++) { scanf("%d", &num[i]); }

int count = 0;
for (i = 0; i < n; i++) {
	for (x = 0; x < n - 1; x++) {
		if (x != i) {
			for (y = x + 1; y < n; y++) {
				if (y != i) {
					if (num[x] + num[y] == num[i]) {
						count++;
					}
				}
			}
		}
	}
}

printf("%d\n", count);
return 0;