from math import sqrt, ceil


def euclidean(x1, x2, y1, y2):
    return sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)


r, x, y, x1, y1 = map(int, input().split())
d = euclidean(x, x1, y, y1)
print(ceil(d / (2 * r)))
