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


using namespace std;

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


int a[900],r,n;

int main()
{
    f>>n;
    for (int i=1;i<=n;i++)
        f>>a[i];
    sort(a+1,a+1+n);
    for (int i=1;i<n-1;i++)
        for (int j=i+1;j<n;j++)
    {
        int k=j+1;
        while (a[i]+a[j]>=a[k] && k<=n)
            {r++;
            //cout<<a[i]<<" "<<a[j]<<" "<<a[k++]<<endl;
            }
    }
    g<<r;

}