def sum_tree(tree):
    l_or_r = True #True = L, False = R
    l_size = 1
    l_gaps = 0
    r_size = 1
    r_gaps = 0
    row = 0
    left_sum = 0
    right_sum = 0
    if tree == []:
        return ''
    for i in range(1, len(tree)):
        if l_or_r == True:
            if tree[i] != -1:
                left_sum += tree[i]
            if tree[i] == -1:
                l_gaps += 1
            l_size -= 1
        else:
            if tree[i] != -1:
                right_sum += tree[i]
            if tree[i] == -1:
                r_gaps += 1
            r_size -= 1

        if l_or_r == True and l_size == 0:
            l_or_r = False
            l_gaps = l_gaps * 2
            l_size = 2 ** (row + 1) - l_gaps
        if l_or_r == False and r_size == 0:
            l_or_r = True
            r_gaps = r_gaps * 2
            r_size = 2 ** row - r_gaps
            row += 1
    print(left_sum)
    print(right_sum)

    if left_sum > right_sum:
        return "Left"
    if right_sum > left_sum:
        return "Right"
    if right_sum == left_sum:
        return ""