/* 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 Main
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        BufferedReader inp=new BufferedReader(new InputStreamReader(System.in));
        String s[] =inp.readLine().split(" ");
        long  r=Long.parseLong(s[0]);
        long x=Long.parseLong(s[1]);
        long y=Long.parseLong(s[2]);
        long x1=Long.parseLong(s[3]);
        long y1=Long.parseLong(s[4]);
    //  System.out.println((x-x1)*(x-x1));
    //  System.out.println((y-y1)*(y-y1));
        long num=(x-x1)*(x-x1) + (y-y1)*(y-y1);
    //  System.out.println(num);
        double ans=Math.sqrt(num);
        double sol=(ans)/(2*r);
    System.out.printf("%.0f",Math.ceil(sol));
        
    }
}