"""
Created on Sun Aug 23 09:45:23 2020

@author: roastedcoder

This is for Codeforces
"""

mod = 1000000007
ssi = lambda : map(int,input().split())

# RoastedCoder

from math import ceil

r, x, y, x1, y1 = ssi()
a = pow(abs(x-x1), 2) + pow(abs(y-y1), 2)
dist = pow(a,0.5)
res = ceil(dist/(2*r))
print(res)