import java.util.*;
import java.io.*;
public class cf11
{
	public static void main(String args[])
	{
		Scanner scan=new Scanner(System.in);
		double r=scan.nextInt(),x0=scan.nextInt(),y0=scan.nextInt(),x1=scan.nextInt(),y1=scan.nextInt(),i=0,f;
		x0=x0-x1;
		y0=y0-y1;
		double step=(int)Math.ceil(Math.sqrt(x0 * x0 + y0 * y0)/(2*r));
		System.out.print((int)step);
	}
}