#include <stdio.h>
#include <algorithm>
using namespace std;
int i,j,l,n,nr,a[801],m;
int cautbin(int s,int d)
{
    int m;
    while(s<=d)

	  {
	     m=(s+d)/2;
          if(a[i]+a[j]>=a[m] && a[i]+a[m]>=a[j] && a[j]+a[m]>=a[i])
          { 
           nr++;
           s=m+1;
           }
           else
           s=m+1;             
          }
    return -1;
}
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
     scanf("%d",&a[i]);
sort(a+1,a+n+1);
   for(i=1;i<=n;i++)
     for(j=i+1;j<=n;j++)
      cautbin(j+1,n);
      printf("%d",nr);
    return 0;
}