def transform_string(s):
    result = []
    i = 0
    length = len(s)
    while i < length:
        # 隐藏前两个字符
        if i + 2 > length:
            result.append('X')
        else:
            result.append('XX')
        i += 2
        if i < length:
            # 保留接下来的三个字符
            result.append(s[i:i + 3])
            i += 3
    return ''.join(result)


if __name__ == '__main__':
    print(transform_string('PRESTIGE MULTI ALLOYS T&C W.L.L'))
    print(transform_string('FAR EASTERN POLYTEX(VIETNAM) LIMITED'))