#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;
int v[801];
int main()
{
 int n,s,f;
 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++)
        {
         f=j+1;
         while(f<=n && v[i]+v[j]>=v[f] && v[i]+v[f]>=v[j] && v[j]+v[f]>=v[i])
              {
               f++;
               s++;
              }
        }
    }
 printf("%d\n",s);
return 0;
}