from math import sqrt
def main():
	r, x, y, a, b = (map(int, input().split()))
	d = sqrt((b - y)**2 + (a - x)**2)
	#print(d, 2*r , d/(2*r))
	if d % (2 * r) == 0:
		print( int(d/(2*r)))
	else:
		print(int(d/(2*r)+1))

	

if __name__ == '__main__':
	main()

