#include <fstream>
#include <algorithm>

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int l[805];

int main()
{
   int n,i,j,k,p=0,s;

   f>>n;
   for(i=1;i<=n;i++) f>>l[i];
   sort(l+1,l+n+1);

   for(i=1;i<n;i++) for(j=i+1;j<=n;j++)  {
     s=l[i]+l[j];
     for(k=n;k>=1;k--) if(l[k]<=s) p++;
                       else break;
     p-=2;

   }

   g<<p;

   f.close();
   g.close();
   return 0;
}