#include <stdio.h>
#include <algorithm>

using namespace std;

int v[900],i,j,n,nr,k,ok=0;

int cautbin(int p, int u)
{
  int mij;
  mij=(p+u)>>1;
  while (p<=u)
  {
      if ((v[mij]<=v[i]+v[j] && v[mij+1]>v[i]+v[j]) || (v[mij]<=v[i]+v[j] && mij==n-1))
		  return mij;
	  else if (v[mij]<=v[i]+v[j] && v[mij+1]<=v[i]+v[j]) 
      {
		  p=mij+1; 
		  mij=(p+u)>>1;
	  }
	  else {
		  u=mij-1; 
		  mij=(p+u)>>1;
		  }  
  }
  return 0;
}

int main()
{
	freopen("nrtri.in","r",stdin);
		
	scanf("%d", &n);
	for (i=0;i<n;++i)
		 scanf("%d", &v[i]);
	sort(v,v+n);
	for (i=0;i<n-2;++i)
    for (j=0;j<n-1;++j)
    {
         if (cautbin(0,n-1)) nr++;
    }

	freopen("nrtri.out","w",stdout);
	printf("%d",nr);
return 0;
}