#include <fstream>
#define nmax 9000
#define valmax 7000
#pragma GCC optimize("Ofast")

using namespace std;

int v[nmax + 1], f[valmax + 1], mod2[nmax + 1];

int main()
{
    ifstream cin ("medie.in");
    ofstream cout ("medie.out");
    int n, i, j, tot = 0;
    cin >> n;
    for (i = 1; i <= n; i++)
        cin >> v[i], f[v[i]]++, mod2[i] = v[i] % 2;
    for (i = 1; i <= valmax; i++)
        for (j = i; j >= 1; j -= 2)
        {
            if (i == j)
                tot += f[i] * (f[i] - 1) / 2 * (f[i] - 2);
            else
                tot += f[i] * f[j] * f[ (i + j) / 2];
        }
    cout << tot;
    return 0;
}