import java.util.Scanner;

/**
 * Created by dgsmoke on 23.01.2015.
 */
public class B1
{
    public static void main(String[] args)
    {
        new B1().start();
    }

    Scanner sc = new Scanner(System.in);

    void start()
    {
        int r = sc.nextInt();
        int x = sc.nextInt();
        int y = sc.nextInt();
        int x1 = sc.nextInt();
        int y1 = sc.nextInt();

        double rast = Math.sqrt(Math.pow(x1-x, 2) + Math.pow(y1-y, 2));
        System.out.print( (int) Math.ceil(rast/(r*2)));
    }
}
