/*Author LAVLESH*/
import java.util.*;

public class solution {
	
	

	public static void main(String args[])
    {
     Scanner in=new Scanner(System.in) ;
		double r=in.nextInt();
		double x=in.nextInt();
		double y=in.nextInt();
		double x1=in.nextInt();
		double y1=in.nextInt();
	x=Math.abs(x-x1);
	y=Math.abs(y-y1);
	
    double	ans=Math.ceil(Math.sqrt(x*x+y*y)/(2*r));		
		System.out.println((int)ans);
  }
}
