#include <fstream>
#include <algorithm>

using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int v[805],i,j,n,st,dr,mid,sol,p,u,s;
int main()
{
   cin>>n;
   for(i=1;i<=n;++i)
   cin>>v[i];
   sort(v+1,v+n+1);
   for(i=1;i<n-1;++i)
   for(j=i+1;j<n;++j)
   {
       p=j+1;
       st=j+1; dr=n;
       while(st<=dr)
       {
           mid=(st+dr)/2;
           if(v[mid]<=v[i]+v[j]) {st=mid+1; sol=mid;}
           else dr=mid-1;
       }
       u=sol;
       s+=(u-p+1);
      // cout<<mid<<" ";
   }
   cout<<s;
   return  0;}