#include<iostream>
#include<fstream>
using namespace std;

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

int N, v[801],i,j,aux,k,contor;


int main()
{
    f>>N;
    for( i=1; i<=N; i++)
          f>>v[i];

    for(i=1; i<=N-1; i++)
        for(j=i+1; j<=N; j++ )
            if(v[i]>v[j]) {aux=v[i]; v[i]=v[j] ;v[j]=aux;}

      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[j]+v[k]>=v[i] && v[k]+v[i]>=v[j]) contor++;
                             else break;

     g<<contor;
     f.close();
     g.close();
     return 0;
}