#include <fstream.h>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n,v[100005];

int main()
{	
	int nn=0,general=0,i,j,k;
	f>>n;
	for(i=1;i<=n;i++)
		f>>v[i];
	sort(v+1,v+n+1);	
	for(i=1;i<n-1;i++)
		for(j=i+1;j<n;j++)		
		{
			k=j+1;
			while(k<=n && v[k]<=(v[i]+v[j])) k++;
			general += k-j-1;
		}
	g<<general<<'\n';
	f.close();
	g.close();
	return 0;
}