import math

inp = list(map(int, input().split()))

rad = (inp[0])
c1, c2 = [inp[1], inp[2]], [inp[3], inp[4]]

sqr = math.ceil(math.sqrt((c1[0] - c2[0])**2 + (c1[1] - c2[1])**2) / (2 * rad))
print(sqr)