#include <fstream>
#include <algorithm>
using namespace std;
int n,s,d,v[801],u1,p1,p,u,nr=0,mij,i,j;
int main()
{ifstream f("nrtri.in");
ofstream g("nrtri.out");
    f>>n;
    for(i=1;i<=n;i++)f>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n-1;i++)
    {for(j=i+1;j<=n;j++)
      {s=v[i]+v[j];d=v[j]-v[i];
          p=j+1;u=n;
          while(p<=u)
          {mij=(p+u)/2;
           if(v[mij]<=s){p=mij+1;}
              else {u=mij-1;}
          }
       p1=j+1;u1=n;
       while(p1<=u1)
       {mij=(p1+u1)/2;
       if(v[mij]<d){p1=mij+1;}
        else {u1=mij-1;}
        }
        nr=nr+(u-p1+1);
      }

    }
    g<<nr;
    return 0;
}