#include<bits/stdc++.h>

using namespace std;

int a[1000],rs,n;

int main() {
	ifstream cin("nrtri.in");
	ofstream cout("nrtri.out");
	cin>>n;
	for (int i=0; i<n; i++) cin>>a[i];
	sort(a,a+n);
	
	for (int i=0; i<n; i++) {
		for (int j=i+1; j<n; j++) {
			for (int l=j+1; l<n; l++) {
			//	cout<<a[i]<<" "<<a[j]<<" "<<a[l];
				if (a[i]+a[j]>=a[l] ) {
					rs++; //cout<<"$\n";
				}
			}
		}
	}
	cout<<rs;
	
	return 0;
}