#include<fstream>
#include<cstdio>
#include<algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int a[802];
int main()
{
	int n,nr=0,i,j,s,dr,k;
	in>>n;
	for(i=1;i<=n;i++) in>>a[i];
	sort(&a[1],&a[n+1]);
	for(i=1;i<n;i++)
		for(j=i+1;j<=n;j++)
		{
			dr=j;
			s=a[i]+a[j];
			for(k=j+1;k<=n &&a[k]<=s;k++) nr++;
		}
	out<<nr;	
	return 0;
}