#include<stdio.h>
#include<algorithm>
using namespace std;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int n,i,a[801],j,x=0;
	scanf("%d",&n);
	for(i=0;i<n;++i) scanf("%d",&a[i]);
	sort(a,a+n);
	for(i=0;i<n-2;++i)
		for(j=i+1;j<n-1;++j)
			x=x+upper_bound(a+j,a+n,a[i]+a[j])-a-j-1;
	printf("%d",x);
	return 0;
}