#include <cstdio>
#include <algorithm>

using namespace std;

int main()
{
	freopen("nrtri.in", "r", stdin);
	freopen("nrtri.out", "w", stdout);
	
	int n, v[801];
	scanf("%d", &n);
	for(int i=1; i<=n; i++) scanf("%d", &v[i]);
	
	sort(v+1, v+n+1);
	
	int ans=0;
	for(int i=1; i<n-1; i++)
	{
		for(int j=i+1; j<n; j++)
		{
			int sum=v[i] + v[j], k=j+1;
			while(v[k] <= sum && k<=n) ans++, k++;
		}
	}
	printf("%d", ans);
}