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

using namespace std;

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

int n, v[1001], i, j, x, nrt;

int main()
{
    in>>n;
    for(i = 1; i <= n; i++) in >> v[i];

    sort(v+1, v+n+1);

    for(i = 1; i <= n-2; i++)
    {
        for(j = i+1; j <= n-1; j++)
        {
            for(x = j+1; x <= n && v[x] <= v[i] + v[j]; x++) nrt++;
        }

    }
    out<<nrt;
    return 0;
}