#B. Amr and Pins: http://codeforces.com/contest/507/problem/B
from sys import stdin, stdout
import math

def main():
	r, x1, y1, x2, y2 = map(int, stdin.readline().split())
	d = math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))
	c = r * 2
	res = (d / c)
	# print res
	# Special Case: res <= 2
	if res == 0:
		print 0
	elif res <= 1:
		print 1
	elif d % c == 0:
		print int(res)
	else:
		print int(res) + 1
main()

