def _bst_new_node(name, phone):
    return {'name': name, 'phone': phone, 'left': None, 'right': None}


def bst_insert(root, name, phone):
    if root is None:
        return _bst_new_node(name, phone)

    if name == root['name']:
        root['phone'] = phone
    elif name < root['name']:
        root['left'] = bst_insert(root['left'], name, phone)
    else:
        root['right'] = bst_insert(root['right'], name, phone)

    return root


def bst_find(root, name):
    if root is None:
        return None

    if name == root['name']:
        return root['phone']
    elif name < root['name']:
        return bst_find(root['left'], name)
    else:
        return bst_find(root['right'], name)


def _bst_min_node(root):
    node = root
    while node['left'] is not None:
        node = node['left']
    return node


def bst_delete(root, name):
    if root is None:
        return None

    if name < root['name']:
        root['left'] = bst_delete(root['left'], name)
    elif name > root['name']:
        root['right'] = bst_delete(root['right'], name)
    else:
        # node found — three cases
        if root['left'] is None:
            return root['right']
        if root['right'] is None:
            return root['left']

        # two children: replace node with in-order successor
        successor = _bst_min_node(root['right'])
        root['name'] = successor['name']
        root['phone'] = successor['phone']
        root['right'] = bst_delete(root['right'], successor['name'])

    return root


def bst_list_all(root):
    if root is None:
        return []
    return bst_list_all(root['left']) + [(root['name'], root['phone'])] + bst_list_all(root['right'])
