import java.util.*;
import java.io.*;
public class Amr_Pins
{
	public static void main(String args[]) throws Exception
	{
		BufferedReader f=new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st=new StringTokenizer(f.readLine());
		long radius=Integer.parseInt(st.nextToken());
		long xpos=Integer.parseInt(st.nextToken());
		long ypos=Integer.parseInt(st.nextToken());
		long xpos_delta=Integer.parseInt(st.nextToken());
		long ypos_delta=Integer.parseInt(st.nextToken());
		double dis=Math.sqrt((xpos-xpos_delta)*(xpos-xpos_delta)+(ypos-ypos_delta)*(ypos-ypos_delta));
		System.out.println((int)Math.ceil(dis/(2*radius)));
	}
}