EX3.3

Imagine a (literal) stack of plates. If the stack gets too high, it
might topple. There- fore, in real life, we would likely start a new
stack when the previous stack exceeds some threshold. Implement a data
structure SetOfStacks that mimics this. SetOf- Stacks should be
composed of several stacks, and should create a new stack once the
previous one exceeds capacity. SetOfStacks.push() and SetOfStacks.pop()
should behave identically to a single stack (that is, pop() should
return the same values as it would if there were just a single stack).
FOLLOW UP
Implement a function popAt(int index) which performs a pop operation on
a specific sub-stack.