Create a mini stack (in c++) that supports push, pop, top, and retrieving the minimum element using two stacks.

push(x) -Push element x onto stack.

pop() -Removes the element on top of the stack.

top() -Get the top element.

getMin() -Retrieve the minimum element in the stack.

Ex.

MinStack minStack;

minStack.push(-1);

minStack.push(0);

minStack.push(-2);

minStack.getMin(); //returns -2

minStack.pop();

minStack.top(); //returns 0

minStack.getMin(); //returns -1