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

using namespace std;

ifstream in ("nrtri.in");
ofstream out ("nrtri.out");

int N, x, k;
vector<int> vect;

int main()
{
    in >> N;
    for(int i = 0; i < N; i++)
    {
        in >> x;
        vect.push_back(x);
    }

    sort(vect.begin(), vect.end());

    for(int i = 0; i < N - 1; i++)
        for(int j = i + 1; j < N; j++)
        {
            int q = j + 1;
            while(vect[i] + vect[j] >= vect[q] && q < N)
            {
                if(q != j)
                    k++;
                q++;
            }
        }
    out << k;
    return 0;
}