#include <fstream>
#include <algorithm>
#include <iostream>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int n,v[3001],i,j,s,q,sol;
int main()
{   fin>>n;
  for(i=1;i<=n;i++)
    fin>>v[i];
 sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
        for(j=i+1;j<=n-1;j++){
            s=v[i]+v[j];
            for(q=j+1;q<=n;q++)
                if(v[q]<=s){
                sol++;
                break;
                }
        }
    fout<<sol;

    return 0;
}