import math
r,x,y,a,b = map(int,input().split())
a = math.sqrt((x-a)**2+(y-b)**2)
if a==0:
	print(0)
elif a%(2*r)==0:
	print(int(a//(2*r)))
elif a<2*r:
	print(2)
else:
	count =0
	x = a-2*r
	while x>2*r:
		count+=1
		x = x-2*r
	print(count+2)