Problem C
Stack

Write your own implementation of a stack, specialized to store $32$-bit signed integers. Stacks are simple and only have a few operations.

The data structure should support the following operations:

• Default construction - initializes an empty stack. This is not tested explicitly here!

• Assignment and copy construction - must properly copy the contents of another instance of the data structure. Ensure the two instances do not share memory afterwards!

• Push - must insert an element on top of the stack.

• Pop - must remove the top element off of the stack.

• Top - must provide access to the top element of the stack.

• Size - must provide the size of the stack.

You must avoid any memory leaks or other memory errors in your implementation.

Input

The input starts with a line containing an integer $q$, representing the number of lines that follow. Each line will represent an operation that is run. The lines have the following format: <id> <operation> [arg]

The instance ID will be an integer from $1$ to $1,000$, representing an instance of the data structure. Each instance should be default initialized at the start as an empty stack.

The operations are the following:

• a - construct a copy of the stack, takes integer argument for the instance ID of the stack to copy

• + - push a value on the stack, takes integer argument for the value to push

• - - pop the stack, no additional arguments

• t - output the top element of the stack, see output section

• s - output size of stack, see output section

You may assume requested operations will not cause an error in a correctly implemented data structure. For example, a pop operation on an empty stack will not occur in the input.

Output

For each top operation, output a line with the top element of the stack.

For each size operation, output a line with the size of the stack.

7
1 + 1
1 t
1 + 2
1 t
1 s
1 -
1 s

1
2
2
1

6
1 + -9
1 + 6
1 + 42
2 + -5
1 s
2 s

3
1