#include <fstream>
using namespace std;
bool comp(int a,int b)
{
	return a<b;
}
int v[800];
int main()
{
	ifstream f("nrtri.in");
	ofstream o("nrtri.out");
	int n,k,i,j;
	long count=0;
	f>>n;
	for (i=1;i<=n;i++)
		f>>v[i];
	sort(v+1,v+n,comp);
	for (i=1;i<n-1;i++)
		for(j=i+1;j<n;j++)
			for (k=j+1;v[k]<v[i]+v[j];k++)
				count++;
	o<<count;
	return 0;
}