// infoarena: problema/nrtri //
#include <fstream>
#include <algorithm>
#define MAXN 810
using namespace std;

ifstream in("nrtri.in");
ofstream out("nrtri.out");

int s,x[MAXN],n,i,j, *p1, *p2;

int main()
{
	in>>n;
	for(i=1; i<=n; i++)
		in>>x[i];
	
	sort(x+1, x+n+1);
	
	for(i=1; i<n-1; i++)
		for(j=i+1; j<n; j++)
		{
			p1 = lower_bound(x+j+1, x+n+1, x[j]-x[i]);
			p2 = upper_bound(x+j+1, x+n+1, x[j]+x[i]);
			
			s += p2 - p1;
		}
		
	out<<s;
	
	return 0;
}