#include<fstream>  
  
using namespace std;  
  
int n,a[800],c;  
  
int main()  
{  int i,j,k;  
   ifstream fin("nrtri.in");  
   ofstream fout("nrtri.out");  
   fin>>n;  
   for(i=1;i<=n;i++)  
           fin>>a[i];  
   for(i=1;i<n-1;i++)  
      for(j=i+1;j<n;j++)  
         for(k=j+1;k<=n;k++)  
         if(a[i]<=a[j]+a[k]&&a[k]<=a[i]+a[j]&&a[j]<=a[i]+a[k]) c++;  
   fout<<c;  
   fin.close();  
   fout.close();  
   return 0;  
}