import math
r, x, y, a, b = [int(p) for p in raw_input().split()]

d = math.sqrt((x-a)**2 + (y-b)**2)
inc = 0
s = float(0)

if x == a and y == b :
	print 0
	exit()

while float(2*r+s) <= d:
	inc += 1
	s += r
print inc 

