# -*- coding: utf-8 -*-
"""
Created on Mon Dec  2 18:52:00 2019

@author: lfy
"""

import math

def pin(r,x,y,x_,y_):
    l=math.sqrt((x_-x)**2+(y_-y)**2)
    a=(l-2*r)/(2*r)
    if a==int(a):
        return int(a+1)
    else:
        return int(a+2)
def main():
    il=input().split()
    print(pin(float(il[0]),float(il[1]),float(il[2]),float(il[3]),float(il[4])))
if __name__=="__main__":
    main()