#include<fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");  
int n,i,j,k,s[800],aux,ok=0;
int main()
{
f>>n;
      for(i=1;i<=n;i++)
         f>>s[i];
           for(i=1;i<=n;i++)
           for(j=i+1;j<=n;j++)
           if(s[i]>s[j])
           {aux=s[i];
           s[i]=s[j];
           s[j]=aux;
           }
               for(i=1;i<=n;i++) 
               for(j=i+1;j<=n;j++)
               for(k=j+1;k<=n;k++)
                if(s[i]+s[j]>=s[k])
                 ok++;
                   g<<ok; 
                    g.close();
                     return 0;
                          }