#include <cstdio>
#include <algorithm>
using namespace std;

#define Nmax 808

int N, i, j, nr, A[Nmax];

int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);

	scanf("%d", &N);
	for (i=0; i<N; ++i)
		scanf("%d", &A[i]);
	sort(A, A+N);

	for (i=0; i<N; ++i)
		for (j=i+1; j<N; ++j)
		{
			int p = upper_bound(A+j+1, A+N, A[i]+A[j]) - A;			
			nr += p - j - 1;
		}

	printf("%d\n", nr);

	return 0;
}