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

int main()
{

	int n, rez, aux1, aux2, k;

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

	scanf("%d", &n);
	int nr[n];

	for(int i = 0; i < n; ++i)
		scanf("%d", &nr[i]);

	sort(nr, nr + n);

	rez = 0;
	for(int i = 0; i < n-2; ++i)
	{
		aux1 = nr[i];
		k = i+2;

		for(int j = i+1; j < n; ++j)
		{
			aux2 = nr[j];

			while(k < n && aux1 + aux2 > nr[k])
				++k;

			rez += k-j-1;
		}
	}

	printf("%d", rez);

	return 0;
}