#include<fstream>
#include<algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
int a[800],n,i,aux;
int rs;
bool comp(int a,int b){
	return a<b;
}
int main(){
	cin>>n;
	for(i=0;i<n;i++)cin>>a[i];
	sort(a,a+n,comp);
	for(i=0;i<n;){
		for(int j=i+1;j<n;)
		{
		aux=j+1;
		while(a[aux]<=(a[i]+a[j])&&aux<n){
			aux++;
			
		}
		rs+=aux-j-1;
		j++;
		}
		i++;	
	}
	cout<<rs;
	return 0;
}