

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

public class apin {

	int rr;
	int xx;
	int yy;
	int xx1;
	int yy1;
	int nn;
	
	public apin() throws Exception
	{
		BufferedReader f = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(f.readLine()); 
		rr = Integer.parseInt(st.nextToken());
		xx = Integer.parseInt(st.nextToken());
		yy = Integer.parseInt(st.nextToken());
		xx1 = Integer.parseInt(st.nextToken());
		yy1 = Integer.parseInt(st.nextToken());
		
	    f.close();  
	}
	
	public void compute()
	{
		int deltax = xx1 - xx;
		int deltay = yy1 - yy;
		int dist = (int)(Math.ceil(Math.sqrt((double)(deltax * deltax + deltay * deltay))));
		nn = dist / (2 * rr);
		int re = dist - nn * 2 * rr;
		if(re > 0)
			++nn;
	}
	
	public void results()
	{
	    System.out.println("" + nn);
	}

  public static void main (String [] args) throws Exception {
	  apin aa = new apin();
    aa.compute();
    aa.results();
  }
}
