# your code goes here
r, x, y, xx, yy = [int(x) for x in input().split()]
steps = 0
dis = (x - xx) ** 2 + (y - yy) ** 2
dis = dis ** 0.5

if dis % 1 != 0 or dis % (2 * r) != 0:
	steps += 1

steps += dis // (2 * r)

print(int(steps))
