import math
l=list(map(int, input().split()))

def f(l):
	r=l[0]
	x=l[1]
	y=l[2]
	a=l[3]
	b=l[4]
	dist=math.sqrt((x-a)**2+(y-b)**2)
	if dist==0:
		return 0
	t=dist/(2*r)
	if t%1==0:
		return int(t)
	return int(t)+1
print(f(l))