#include<fstream>
#include<algorithm>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");
int n,i,k,A[801],j,rez;
int main()
{
	fi>>n;
	for(i=1; i<=n; i++)
		fi>>A[i];
	sort(A+1,A+n+1);
	for(i=1; i<n; i++)
	{
		k=i+2;
		for(j=i+1; j<=n; j++)
		{
			while(k<=n && A[k]<=A[i]+A[j])
			{
				k++;
			}
			if(k-j-1>0)
				rez=rez+k-j-1;
		}
	}
	fo<<rez<<"\n";
	fi.close();
	fo.close();
	return 0;
}