Find a Node by Index and by Value

A linked list has no random access, so both lookups are the same walk with a different stopping rule: one counts steps, the other compares values.

Requirements:
1. getAt(int index) returns the value at that 0-based position, or -1 when the index is negative or past the end.
2. indexOf(int value) returns the 0-based position of the first node holding value, or -1 when no node holds it.

The Node class is provided - do not rename it and do not add public to it, because a Java source file may contain only one public class.

Do NOT write a main method.