import java.util.*;

import java.lang.*;
// import java.math.*;
import java.io.*;
public class Main
{
    public static int mod=(int)Math.pow(10,9) + 7;
    public static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    public static PrintWriter ot=new PrintWriter(System.out);
    public static int[] take_arr(int n){
        int a[]=new int[n];
        try {
            String s[]=br.readLine().trim().split(" ");
            for(int i=0;i<n;i++)
            a[i]=Integer.parseInt(s[i]);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return a;
    }
	public static void main (String[] args) throws java.lang.Exception
	{
		try{
            int t=1;//Integer.parseInt(br.readLine().trim());
            int cno=1;
            while(t-->0)
            {
                String qq[]=br.readLine().trim().split(" ");
                int r=Integer.parseInt(qq[0]);
                int x1=Integer.parseInt(qq[1]);
                int y1=Integer.parseInt(qq[2]);
                int x2=Integer.parseInt(qq[3]);
                int y2=Integer.parseInt(qq[4]);
                r*=2;
                double dist=Math.sqrt(Math.pow(x2-x1, 2)+Math.pow(y2-y1, 2));
                // ot.println(dist);
                // dist=Math.sqrt(dist);
                // ot.println(dist);
                ot.println((int)Math.ceil(dist/r));
                
            }
            ot.close();
            br.close();
            
        }catch(Exception e){
            e.printStackTrace();
            return;
        }
    }
  
}

    