#include <iostream>

#define NMAX 7000

using namespace std;

int v [ NMAX + 1 ] ;

int main() {

  FILE *fin, *fout ;
  fin = fopen ("medie.in", "r" ) ;
  fout = fopen ("medie.out", "w" ) ;
  int n, i, a, prod, j ;
  fscanf (fin, "%d", &n ) ;
  for (i = 0 ; i < n ; i++ ) {
    fscanf (fin, "%d", &a ) ;
    v[a]++;
  }
  prod = 0 ;
  for (i = 1 ; i < NMAX ; i++ ) {
    if (i % 2 == 0 ) {
      for (j = 0 ; j < i ; j+=2 )
        prod += (v[i] * v[j] * v[(i+j)/2] ) ;
    }
    else {
      for (j = 1 ; j < i ; j+=2 )
        prod += (v[i] * v[j] * v[(i+j)/2] ) ;
    }
    prod += v[i] * (v[i]-1) * (v[i]-2) / 2 ;
  }
  fprintf (fout, "%d", prod ) ;
  return 0;
}