import math
input_list = input().split()
r = int(input_list[0])
x_o = int(input_list[1])
y_o = int(input_list[2])
x_d = int(input_list[3])
y_d = int(input_list[4])
distance = math.sqrt(math.pow((x_o-x_d), 2)+math.pow((y_o-y_d), 2))

step = math.ceil(distance/(2*r))

print(step)
