#include <fstream>

using namespace std;
int f[7005], v[9005];
int main()
{
    ifstream cin("medie.in");
    ofstream cout("medie.out");
    int n, a, h = 1, cnt = 0, cz;
    double p;
    cin >> n;

    for(int i = 1; i <= n; i++)
    {
        cin >> v[i];
        f[v[i]]++;
    }

    for(int i = 1; i <= 7005; i++)
    {
        for(int j=i; j>=1; j-=2)
		{
			if(i==j)
			{
				cnt+= f[i]*(f[j]-1)/2*(f[i]-2);
			}
			else
			{
				cnt+=f[i]*f[j]*f[(i+j)/2];
			}
		}
    }

    cout << cnt;
    return 0;
}