import math
s = raw_input()
l = s.split(' ')
r = float(l[0])
x1 = int(l[1])
y1 = int(l[2])
x2 = int(l[3])
y2 = int(l[4])
d = math.sqrt((x1-x2)**2+(y1-y2)**2)
if d/(2*r)!=int(d/(2*r)):
	print int(d/(2*r))+1
else:
	print int(d/(2*r))