class BinaryTree():
    def __init__(self,item):
        self._root=item
        self._left=None
        self._right=None

    def isEmpty(self):
        return self._root==None

    def setLeft(self,subtree):
        self._left=subtree

    def setRight(self,subtree):
        self._right=subtree

    def setRoot(self,item):
        self._root=item

    def getLeft(self):
        return self._left

    def getRight(self):
        return self._right

    def getRoot(self):
        return self._root

    def removeLeft(self):
        temp = self._left
        self._left=None
        return temp

    def removeRight(self):
        temp = self._right
        self._right = None
        return temp

    def getPostFix(self):
        output = ""
        if self._left != None:
            output += self._left.getPostFix()
        if self._right != None:
            output += self._right.getPostFix()
        output += str(self._root)
        return output