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

using namespace std;

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

int main()
{
    int n,v[805], c=0;
    in>>n;
    for(int i=1;i<=n;i++)
        in>>v[i];
    sort(v+1,v+1+n);
    for(int i=1;i<=n;i++)
    {
        for(int j=i+1;j<=n;j++)
        {
            for(int z=j+1;z<=n;z++)
        {

            if(v[i]+v[j]<=v[z])
                c++;
            else break;

        }
        }
    }
    out<<c;
    return 0;
}