eps = 1e-7
from math import *
r, x, y, x1, y1 = map(int, input().split())
d = sqrt((x - x1) ** 2 + (y - y1) ** 2)
if d < eps:
    print(0)
elif d - eps < r:
    print(1)
else:
    d -= r
    print(ceil(d / (2 * r)) + 1)