#include "stdio.h"

int N, a[900], nr;
FILE *f, *g;

int main()
{
	f = fopen("nrtri.in", "r");
	g = fopen("nrtri.out", "w");

	nr = 0;

	fscanf(f, "%d", &N);
	for(int i = 1; i <= N; i++)
		fscanf(f, "%d", &a[i]);

	for(int i = 1; i <= N-1; i++)
		for(int j = i+1; j <= N; j++)
		{
			if(a[i] > a[j])
			{
				int aux = a[i];
				a[i] = a[j];
				a[j] = aux;
			}
		}

	for(int i = 1; i <= N-2; i++)
		for(int j = i+1; j <= N-1; j++)
			for(int k = j+1; k <= N; k++)
			{
				if(a[k] <= a[i] + a[j])
					nr = nr + 1;
				else
					break;
			}

	fprintf(g, "%d", nr);

	fclose(f);
	fclose(g);

	return 0;
}