import java.util.*;

/**
 *
 * @author greggy
 */
public class AmrAndPins {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int r = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();

        double distance = Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));
        int ans = (int) Math.ceil(distance / (2.0 * r));
        System.out.println(ans);
    }

}