import itertools
import math

ni = lambda: int(raw_input())
na = lambda: raw_input().split()
nai = lambda: map(int, na())
naf = lambda: map(float, na())

r, x, y, x1, y1 = nai()
dx = x - x1
dy = y - y1
dx, dy = abs(dx), abs(dy)
dist = math.ceil(math.sqrt(dx ** 2 + dy ** 2))
r = r * 2
total_circles = dist % r
to_add = dist / r
# print "DIST: ", dist, " R: ", r, " tot: ", total_circles, " to_add ", to_add
if total_circles:
    to_add += 1

print int(to_add)