#include <stdio.h>
#include <algorithm>
using namespace std;

int main()
{
	int n,v[810];
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	int i;
	for(i=1;i<=n;i++){
		scanf("%d",&v[i]);
	}
	sort(v+1,v+n+1);
	int j,k,s=0;
	for(j=n;j>=3;j--){
		k=j-1;
		for(i=1;i<k;i++){
			while(v[i]+v[k]>=v[j] && i<k){
				s=s+1;
				k--;
			}
		}
	}
	printf("%d",s);
	return 0;
}