#include <iostream>
#include <fstream>
#define NMAX 801
using namespace std;

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

int n,a[NMAX],contor;

int main()
{
    in >> n;
    for(int i=0;i<n;i++)
    {
        in >> a[i];
    }

    for(int i=0;i<n;i++)
    {
        for(int j=i+1;j<n;j++)
        {
            for(int k=j+1;k<n;k++)
            {
                if(a[i]+a[j]>=a[k] && a[i]+a[k]>=a[j] && a[j]+a[k]>=a[i])
                {
                    contor++;
                  //  cout << i << " " << j << " " << k <<endl;
                }
            }
        }
    }

    out << contor;
    return 0;
}