class BSTNode: def __init__(self, val=None): self.left = None self.right = None self.val = val

def insert(self, val):
    if not self.val:
        self.val = val
        return

    if self.val == val:
        return

    if val < self.val:
        if self.left:
            self.left.insert(val)
            return
        self.left = BSTNode(val)
        return

    if self.right:
        self.right.insert(val)
        return
    self.right = BSTNode(val)

def get_min(self):
    current = self
    while current.left is not None:
        current = current.left
    return current.val

def get_max(self):
    current = self
    while current.right is not None:
        current = current.right
    return current.val

def delete(self, val):
    if self == None:
        return self
    if val < self.val:
        if self.left:
            self.left = self.left.delete(val)
        return self
    if val > self.val:
        if self.right:
            self.right = self.right.delete(val)
        return self
    if self.right == None:
        return self.left
    if self.left == None:
        return self.right
    min_larger_node = self.right
    while min_larger_node.left:
        min_larger_node = min_larger_node.left
    self.val = min_larger_node.val
    self.right = self.right.delete(min_larger_node.val)
    return self

def exists(self, val):
    if val == self.val:
        return True

    if val < self.val:
        if self.left == None:
            return False
        return self.left.exists(val)

    if self.right == None:
        return False
    return self.right.exists(val)

def preorder(self, vals):
    if self.val is not None:
        vals.append(self.val)
    if self.left is not None:
        self.left.preorder(vals)
    if self.right is not None:
        self.right.preorder(vals)
    return vals

def inorder(self, vals):
    if self.left is not None:
        self.left.inorder(vals)
    if self.val is not None:
        vals.append(self.val)
    if self.right is not None:
        self.right.inorder(vals)
    return vals

def postorder(self, vals):
    if self.left is not None:
        self.left.postorder(vals)
    if self.right is not None:
        self.right.postorder(vals)
    if self.val is not None:
        vals.append(self.val)
    return vals