def sum_lists(list):
    res = 0
    for elem in list:
        if str(elem).isdigit():
            res = res + elem
        else:
            res = res + sum_lists(elem)
    return res
list1 = [1, 2, [2, 4, [[7, 8], 4, 6]]]
result = sum_lists(list1)
print("Result = ", result)