// Project: Recursion
// Module: trace2
// Source code file: Main.java

// Practice problem: Draw the recursion tree, then predict the output.

public class Main {
    public static void main(String[ ] args) {
        f(3);
    }

    public static void f(int n) {
        if (n > 0) {
            System.out.print(n + " ");
            f(n - 1);
            System.out.print(n + " ");
            f(n - 2);
            System.out.print((n + 1) + " ");
        }
    }
}