#include<iostream>
#include<fstream>
#include<algorithm>
using namespace std;
int a[99],i,j,n,m,re,l1,l2;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int main()
{
	fin>>n;
	for(i=1; i<=n; ++i)
	fin>>a[i];
	sort(a+1, a+n+1);
	for(i=1; i<=n-2; ++i)
	{
		for(j=i+1;j<=n-1;++j)
		{
			l2=j+1;
			l1=n;
			while(l2<=l1)
			{
				m=(l1+l2)/2;
				if(a[m]>a[i]+a[j])
					l1=m-1;
				else
					l2=m+1;
			}
			re+=l1-j;
		}
	}
	fout<<re;
	fin.close();
	fout.close();
	return 0;
	
}