/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        Scanner sc = new Scanner(System.in);
        long r = sc.nextLong();
        long x = sc.nextLong();
        long y = sc.nextLong();
        long xx = sc.nextLong();
        long yy = sc.nextLong();
        long d = (x-xx)*(x-xx)+(y-yy)*(y-yy);
        System.out.println((long)Math.ceil(Math.sqrt((double)d/(double)r/(double)r/(double)4)));
    }
}