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

					  	 				  		  							 	