def get_chain(root, val, chain):
    if not root:
        return None
    if root.info == val:
        chain = chain + (root,)
        return chain
    left_result = get_chain(root.left, val, chain)
    if left_result:
        return left_result + (root,)
    right_result = get_chain(root.right, val, chain)
    if right_result:
        return right_result + (root,)
    return chain


def lca(root, v1, v2):
    x = get_chain(root, v1, ())
    y = get_chain(root, v2, ())
    x = list(x)
    y = set(y)
    common = None
    for i in range(len(x)):
        if x[-(i+1)] in y:
            common = x[-(i+1)]
    return common