#include<stdio.h>
#include<cstdio>
#include<algorithm>
using namespace std;
int v[813],n,i,nr=0,k;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d", &n);
	for(i=1;i<=n;++i)
		scanf("%d ", &v[i]);
	sort(v+1,v+n+1);
	for(i=1;i<=n-2;++i)
		for(int j=i+1;j<=n-1;++j)
		{
			for(k=j+1;k<=n && v[i]+v[j]>=v[k];++k);
			nr+=k-j-1;
		}
	printf("%d", nr);
	return 0;
}