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

public class Prb{

    static PrintWriter pw;
    static Scanner sc;
    
    static void print(final String arg) {
      pw.write(arg);
      pw.flush();
    }

    static void println(final String arg) {
      pw.write(arg+"\n");
      pw.flush();
    }

    static void print(final int arg) {
      pw.write(arg);
      pw.flush();
    }    

    static void runFile() throws Exception {

      sc = new Scanner(new FileReader("input.txt"));
      pw = new PrintWriter(new BufferedWriter(new FileWriter("output.txt")));

    }

    static void runIo() throws Exception  {

      pw =new PrintWriter(System.out);
      sc = new Scanner(System.in);

    }    
 


	public static void main(String[] args)  throws Exception {


         // runFile();

         runIo();   
 	
         long r  = sc.nextLong();
         long x1 = sc.nextLong();
         long y1 = sc.nextLong();
         long x2 = sc.nextLong();
         long y2 = sc.nextLong();
  
         long ans = Math.abs(x1-x2)*Math.abs(x1-x2) + Math.abs(y1-y2)*Math.abs(y1-y2) ;

         ans = (long)Math.ceil( Math.sqrt(ans) / ((double)2*(double)r) );

		 print(  ans +"");


    }
                        
   


}