Min Stack Design

You are required to design a stack data structure that supports the following operations:

• push(x): Add an integer x onto the stack.
• pop(): Remove the element from the top of the stack. If the stack is empty, do nothing.
• getMin(): Retrieve the minimum element in the stack. If the stack is empty, return -1.

Internally, you must design your data structure such that the getMin operation can be performed in constant time. This is a typical design problem where you may need to maintain an auxiliary structure.

In mathematical terms, if the stack stores a sequence \( s_1, s_2, \ldots, s_n \), then: \[ getMin() = \min_{1 \leq i \leq n} s_i \]

You will be provided with a series of commands to operate on the stack. The input will be given via standard input and the output via standard output.

inputFormat

The first line of input contains a single integer n which represents the number of operations to be performed on the stack. Each of the following n lines contains a command in one of the following formats:

• push x — where x is an integer to be pushed onto the stack.
• pop — which removes the top element of the stack.
• getMin — which prints the minimum element in the stack.

It is guaranteed that the commands are valid. For any getMin command on an empty stack, print -1.

outputFormat

For each getMin command, output the corresponding minimum element on a new line. If the stack is empty during a getMin operation, output -1.

## sample

10
push 3
push 5
getMin
push 2
push 1
getMin
pop
getMin
pop
getMin

3
1
2
3

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