import math

while True:
    try:
        r, x, y, x1, y1 = map(int, input().split())

        distance = math.sqrt((x - x1) ** 2 + (y - y1) ** 2)

        cnt = math.ceil(distance / (2 * r))  # 直接计算需要的步数，使用向上取整

        print(cnt)
    except:
        break