import math
cor = [int(x) for x in input().split()]
r = cor[0]
d = math.sqrt((cor[1] - cor[3]) ** 2 + (cor[2] - cor[4]) ** 2)
if d % (2 * r) == 0:
    print(int(d / (r * 2)))
else:
    print(int(d / (r * 2)) + 1)