import math

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

def distance(x1, x2, y1, y2):

    b1 = (y2 - y1)**2
    b2 = (x2 - x1)**2

    return (math.sqrt(b1 + b2))

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

one_move = 2*r

print(math.ceil(d / one_move))

