DesignStackQueue
Build a last-in-first-out stack using only queue operations. You are given a list of operations to run: push x adds x on top, pop removes and reports the top, top reports the top without removing it, and empty reports whether the stack is empty.
Input
Line 1: q, the number of operations. Next q lines: push x, pop, top or empty.
Output
For every pop and top print the value, and for every empty print true or false, one per line. Operations are always valid.
Constraints
1 <= q <= 10^4 1 <= x <= 99
Example 1
Input
5 push 1 push 2 top pop empty
Output
2 2 false
top shows 2, pop removes 2, and 1 is still in the stack so empty is false.