import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;
public class m7 {
public static void main(String args[])
{
	Scanner s=new Scanner(System.in);
	int r=s.nextInt();
	int x=s.nextInt();
	int y=s.nextInt();
	int xd=s.nextInt();
	int yd=s.nextInt();
	 double d = Math.sqrt(Math.pow(yd - y, 2.0) + Math.pow(xd - x, 2.0));
	   double v=Math.ceil(d / r / 2);
	   int k=(int)v;
	   System.out.println(k);
}
}