#!/usr/local/bin/python3.4

def solution(T):
    if T is None:
        return []
    else:
        result = [T[0]]
        if T[1] is not None:
            l = solution(T[1])
            for node in l:
                if node >= T[0]:
                    result.append(node)
        if T[2] is not None:
            r = solution(T[2])
            for node in r:
                if node >= T[0]:
                    result.append(node)
        return result

T = (5, (3, (20, None, None), (21, None, None)), (10, (1, None, None), None))

print(solution(T))