import math

q, x1, y1, x2, y2 = list(map(int,input().split()))

def distance(args):
  x1, x2, y1, y2 = args
  return math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)

d = distance([x1, x2, y1, y2])

if d == 0:
  print(0)
else:
  print(math.ceil(d / (2 * q)))

 	 	  		   			 				   		 				 	