from __future__ import division
__author__ = 'Moustapha Saad'
r, x, y, xt, yt = map(int,raw_input().split())
distance = pow((pow(abs(yt-y),2)+pow(abs(xt-x),2)),0.5)
ans = int(distance/r)
if x == xt and y == yt:
    print 0
elif distance < r:
    print 1
else:
    print ans-1
