import math
arr = [int(x) for x in input().split()]
r = arr[0]
x1 = arr[1]
y1 = arr[2]
x2 = arr[3]
y2 = arr[4]
resp = math.sqrt(math.pow(y2 - y1, 2) + pow(x2 - x1, 2))
resp = math.ceil((resp / r) / 2)
print (resp)
  			 	 		  			  	  		     				