#include<fstream>
#include<stdlib.h>
using namespace std;
int b[801];

int comp(const void *a,const void *b)
{
	int *pa,*pb;
	pa=(int*)a;
	pb=(int*)b;
	return pb-pa;
}


ifstream in("nrtri.in");
ofstream out("nrtri.out");


int main()
{
	int n,i,j,k,lim,nr=0;
	in>>n;
	for(i=1;i<=n;++i)
		in>>b[i];
	sort(b,b+n+1);
	for(i=1;i<=n-2;++i)
		for(j=i+1;j<=n-1;++j)
		{
			lim=b[i]+b[j];
			for(k=j+1;b[k]<=lim&&k<=n;++k)
				++nr;
		}
	out<<nr;
	return 0;
}