# include <fstream>
# define DIM 7010
using namespace std;
ifstream fin("medie.in");
ofstream fout("medie.out");
int f[DIM],n,i,j,x;
long long sol;
int main () {
    fin>>n;
    for(i=1;i<=n;i++){
        fin>>x;
        f[x]++;
    }
    for(i=1;i<=DIM-5;i++){
        sol+=f[i]*(f[i]-1)*(f[i]-2)/2;
        for(j=i+1;j<=DIM-5;j++)
            if(i%2==j%2)
                sol+=f[i]*f[j]*f[(i+j)/2];
    }
    fout<<sol<<"\n";
    return 0;
}