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

using namespace std;
int i,k,n,v[805],j,p;
int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");

    f>>n;

    for (int i=1; i<=n; i++) f>>v[i];

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

        for (int i=1; i<=n-2; i++)
            for (int j=i+1; j<=n-1; j++)
                for (int p=j+1; p<=n; p++)
                    if (v[i]+v[j]>=v[p]) k++;
                                         else break;

    g<<k;

    return 0;
}