from math import *

a=[int(x) for x in input().split()]
r=a[0]
x1=a[1]
y1=a[2]
x2=a[3]
y2=a[4]

x=sqrt((x1-x2)**2+(y1-y2)**2)
if x1==x2 and y1==y2:
	print(0)
elif x<2*r:
	print(1)
else:
	ans=ceil((x-2*r)/(2*r))
	print(ans+1)