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

int main()
{
  ifstream f("nrtri.in");
  ofstream g("nrtri.out");
  int n, a[850],i,j,l,k=0,s,aux;
  f>>n;
  for(i=1;i<=n;i++)
    f>>a[i];
  for(i=1;i<=n;i++)
    for(j=2;j<=n;j++)
      if(a[i]>a[j])
      {
        a[i]=aux;
        a[i]=a[j];
        a[j]=aux;
      }
    aux=n;
    for(i=1;i<=n;i++)
      { l=a[aux];
        for(j=i+1;j<=n;j++)
          if(a[i]+a[j]<l)k++;
        aux--;
      }

  g<<k;

}