#include <iostream>
#include <fstream>
#include <algorithm>

#define NMAX 810

using namespace std;

ifstream fin("ntri.in");
ofstream fout("ntri.out");

int v[NMAX];
int n;

int main()
{
    fin >> n;
    for (int i = 0; i < n; ++i)
        fin >> v[i];

    sort(v, v + n);
    int rez = 0;
    //mi-e lene
    for (int i = 0; i < n; ++i)
        for (int j = i + 1; j < n; ++j)
            for (int k = j + 1; k < n; ++k)
                if (v[k] <= v[i] + v[j])
                    rez++;

    fout << rez;

    return 0;
}