.NET – uses a CLR type on a Visual Basic key (such as `string`) (for example,` system.string` or `[string]`) Do you have any imagination?

We all know that in C#, there is no difference whether you use String (CLR class) or string (C# keyword). For more information, please refer to the following question

> What is the difference

What is it in the 2019 South China University of Technology? Is there any empty? Can you come to alchem? (Thinking of thinking)

https://ac.nowcoder.com/acm/contest/625/B

Analysis:

All status is only 1<< 18, so we can preprocess f[u][j], and then build a state diagram of all the states that u can transfer;