#include<iostream>
#include<fstream>
using namespace std;

int n, a[810];

void citire(){
	ifstream in("nrtri.in");
	in>>n;
	int i;
	for(i=1;i<=n;i++)
		in>>a[i];
}

int proces(){
	int i,j,k,nr=0;
	for(i=1;i<=(n-2);i++)
		for(j=(i+1);j<=(n-1);j++)
			for(k=(j+1);k<=n;k++)
				if((a[i]+a[j])>=a[k] and (a[i]+a[k])>=a[j] and (a[j]+a[k])>=a[i])
					nr++;
	return nr;
}

int main(){
	citire();
	ofstream out("nrtri.out");
	out<<proces();
	out.close();
	return 0;
}