#include<stdio.h>

long a[800],n,i,j,k,numar;

int main()
{

freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);

scanf("%ld",&n);

for(i=0;i<n;i++)
	    scanf("%ld",&a[i]);

for(i=0;i<n-2;i++)
 for(j=i+1;j<n-1;j++)
  for(k=j+1;k<n;k++)
	  if((a[i]+a[j]>=a[k])&&(a[i]+a[k]>=a[j])&&(a[j]+a[k]>=a[i])) numar++;



printf("%ld",numar);

return 0;
}