import math #.sqrt
def ceil (a, b):
    return -(-a // b)
def answer(r, x, y, xp, yp):
    d = math.sqrt((xp-x)**2 + (yp-y)**2)
    num_rs = ceil(d, 2*r)

    return int(num_rs)

def main():
    r, x, y, xp, yp = [int(i) for i in input().split()]
    print(answer(r, x, y, xp, yp))


    return
main()