#include<stdio.h>
long nr;
int x[801],n,i,j,z;

int main ()
{
freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);
scanf("%d",&n);
for(i=1;i<=n;i++)
	scanf("%d",&x[i]);
for(i=1;i<=n;i++)
   for(j=i+1;j<=n;j++)
   { for(z=j+1;z<=n;z++)
		{
		 if(x[i]+x[j]>=x[z] && x[j]+x[z]>=x[i] && x[i]+x[z]>=x[j])
			 nr++;
		}
   }
   printf("%ld",nr);
return 0;
}