import math
r, x1, y1, x2, y2 = map(int, raw_input().split())


def distance(x1, y1, x2, y2):
    return math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

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

print int(-(- d // (2 * r)))

