#include<fstream>
using namespace std;
int main()
{ 
     int n,i,j,k,v[805],aux,contor=0;
     ifstream f("nrtri.in");
     ofstream g("nrtri.out");
     f>>n;
     for(i=1;i<=n;i++)
     f>>v[i];
     for(i=1;i<=n;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;i++)
        for(j=i+1;j<=n;j++)
           for(k=j+1;k<=n;k++)
              if(v[i]+v[j]>=v[k])
                contor++;
     g<<contor;  
     g.close(); 
    return 0;
}