#include<fstream>
#include<iostream>
#include<vector>
using namespace std;
int a[7012];
int maxim, perechi;
int main(void)
{
	int n;
	FILE *f=fopen("medie.in","rt");
	FILE *g=fopen("medie.out","wt");
	fscanf(f,"%d",&n);
	int i,j,x;
	for (i=1;i<=n;i++)
	{
		fscanf(f,"%d",&x);
		a[x]++;
		if (x>maxim)
			maxim=x;
	}

	for (i=1;i<=maxim;i++)
	{
		for (j=i+2;j<=maxim;j=j+2)
			perechi+=a[i]*a[j]*a[(i+j)/2];
		perechi+=(a[i]-1)*a[i]*(a[i]-2)/2;
	}
	fprintf(g,"%d",perechi);
}