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

using namespace std;

int x[801];

int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    int n,rezultat=0;
    f>>n;
    for(int i = 1 ; i <= n ; ++i)
        f>>x[i];
    sort(x+1, x+n+1);
    for (int i = 1 ; i <= n - 2 ; ++i)
       for (int j = i + 1 ; j < n ; ++j)
          for (int k = j + 1 ; k <= n ; ++k){
            if (x[k] <= x[i] + x[j])
                ++rezultat;
            else
                k = n;
          }
    g<<rezultat;
    f.close();
    g.close();
    return 0;
}