from math import ceil


def main():
    r, x0, y0, x1, y1 = map(int, input().split())

    d = ((x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1)) ** 0.5
    ans = ceil(d / 2 / r)
    print(ans)


main()
