#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;
int v[801];
int main()
{
 int n,s,st,dr,mij,q,rasp;
 freopen("nrtri.in","r",stdin);
 freopen("nrtri.out","w",stdout);
 scanf("%d",&n);
 for(int i=1;i<=n;i++)
    {
     scanf("%d",&v[i]);
    }
 sort(v+1,v+n+1);
 s=0;
 for(int i=1;i<=n;i++)
    {
     for(int j=i+1;j<=n;j++)
        {
         st=j+1;
         dr=n;
         q=v[i]+v[j];
         rasp=0;
         while(st<=dr)
              {
               mij=(st+dr)/2;
               if(v[i]+v[j]>=v[mij] && v[i]+v[mij]>=v[j] && v[j]+v[mij]>=v[i])
                  {
                   dr=mij-1;
                   //if(v[i]+v[j]>=v[mij] && v[i]+v[mij]>=v[j] && v[j]+v[mij]>=v[i])
                      rasp=mij;
                  }
               else
                   st=mij+1;
              }
         if(/*v[rasp]>=q &&*/ v[i]+v[j]>=v[rasp] && v[i]+v[rasp]>=v[j] && v[j]+v[rasp]>=v[i])
            {
             s++;
            }
        }
    }
 printf("%d\n",s);
return 0;
}