import math


[r, x1, y1, x2, y2] = map(int, raw_input('').split(' '))
distance = math.sqrt(pow(y2 - y1, 2) + pow(x2 - x1, 2))
if (distance % (2 * r)) == 0:
    print int(distance / (2 * r))
else:
    print (int(distance / (2 * r)) + 1)
