#include <fstream>
using namespace std;
  int n,i,j,nr,aux,k,a[1000];
  int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
     f>>n;
     
   for(i=1;i<=n;i++)
     f>>a[i];
   for(i=1;i<=n-1;i++)
       for(j=i+1;j<=n;j++)
        if(a[i]>a[j])
{
     aux=a[i];
     a[i]=a[j];
     a[j]=aux;
}
     for(i=1;i<=n;i++)
         for(j=i+1;j<=n;j++)
             for(k=j+1;k<=n;k++)
                 if(a[i]+a[j]>=a[k])   
                  nr++;
                 g<<nr;
                 return 0;
                 }