#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;
}