def merge_lists(a, b):
    """
    Merge lists - e.g.,
    [1, 2, 3, 4, 5, 6] & ['a', 'b', 'c']
    => [1, 'a', 2, 'b', 3, 'c', 4, 5, 6]
    :param a: List a
    :param b: List b
    :return: Merged lists
    """
    result = []
    length = min([len(a), len(b)])
    for i in range(length):
        result.append(a[i])
        result.append(b[i])
    result += a[length:] + b[length:]
    return result