I'm very new to programming, just learned it in university. I have a task where I have to solve this problem recursively in java (without using arrays, if, else, while, etc...)

So the task is to sort numbers from 13542 to 12345.

```
public static void main(String[] args) {
    System.out.println(sort(13542));

}

public static long sort(long n) {
    return n < 10
            ? n
            : sort(n, 0);
}

public static long sort(long n1, long n2) {
    return n1 > 10
            ? xxx
            : xxx;
}

```

The problem is that I have no idea what to do. I think my start is okay, but I have problems with the second method.