#include<iostream>
using namespace std;
int n;
int s[10000]; 
int main(){
	cin >> n;
	int h = 0;
	for(int i = 1;i <= n;i++){
	    cin >> s[i];
	}
	for(int a = 1;a <= n - 2;a ++){
		for(int b = a;b <= n - 2;b++){
			for(int c = b - a;c <= n - 2;c++){
				for(int d = c - b - a;d <= n - 2;d ++){
					if((a + b) == c && (a + b) == d){
						h ++;
					}
				}
			}
		}
	}
	cout << h;
	return 0;
}