classMinStack() {

privateclassNode(var `val`:Int,varmin:Int,varnext:Node?)

privatevar head:Node?=null

funpush(x:Int) {

if(head==null) head=Node(x,x,null)else head=Node(x, min(x,head?.min!!),head)

privateval stack=Stack<Int>()

privateval minStack=Stack<Int>()

funpush(`val`:Int) {

val currentMin=if (minStack.isNotEmpty()) minStack.peek()elseInteger.MAX_VALUE

val newMin= minOf(currentMin, `val`)

stack.push(`val`)

minStack.push(newMin)

}

funpop() {

head= head?.next

if (stack.isNotEmpty()) {

stack.pop()

minStack.pop()

}

}

funtop():Int? {

return head?.`val`

funtop():Int {

return stack.peek()

}

fungetMin():Int? {

return head?.min

fungetMin():Int {

return minStack.peek()

}

}