#include <iostream>
#include <fstream>

using namespace std;

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

int n,v[805],i,j,ct,k;

int main()
{
    in>>n;

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

    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++)
            for(k=j+1;k<=n;k++)
                if(v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i])
                ct++;

    out<<ct;


    return 0;
}