import java.util.*;
import java.lang.*;
import java.io.*;

class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
	    /*
	        number of unordered quadruplets (i,j,k,l) such that b[i] + b[j] + b[k] + b[l] = 0
	        ~ code by roshanadhav
	    
	    */
	    
	    
	    //O(n^4) ;
	    Scanner sc = new Scanner(System.in) ; 
	    int n = sc.nextInt() ; 
	    int arr[] = new int[n] ; 
	    
	    for(int i = 0 ; i < n ; i++) {
	        arr[i] = sc.nextInt() ; 
	    }
	    
	    for(int i = 0 ; i < n ; i++) {
	        for(int j = i + 1 ; j < n ; j++) {
	            for(int k = j + 1 ; k < n ; k++) {
	                for(int l = k+1 ; l < n ; l++) {
	                    if(arr[i] + arr[j] + arr[k] + arr[l] == 0) count++ ; 
	                }
	            }
	        }
	    }
	    
	    System.out.println(count);
	}
}