#
# Uian Sol Gorgonio <sol.uian@gmail.com>
# Feb 11 2015
# Amr and Pins
# http://codeforces.com/contest/507/problem/B
#
# geometry
#

import math

r, x1, y1, x2, y2 = map(int, raw_input().split())

d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)

print int(math.ceil(d / (2*r)))
