Time Limit: 1000 ms Memory Limit: 10000 KiB
In the land of Hedonia the official language is Hedonian. A Hedonian
professor had noticed that many of her students still did not master
the syntax of Hedonian well. Tired of correcting the many syntactical
mistakes, she decided to challenge the students and asked them to
write a program that could check the syntactical correctness of any
sentence they wrote. Similar to the nature of Hedonians, the syntax of
Hedonian is also pleasantly simple. Here are the rules:
0. The only characters in the language are the characters p through z
and N, C, D, E, and I.
1. Every character from p through z is a correct sentence.
2. If s is a correct sentence, then so is Ns.
3. If s and t are correct sentences, then so are Cst, Dst, Est, and
4. Rules 0. to 3. are the only rules to determine the syntactical
correctness of a sentence.
You are asked to write a program that checks if sentences satisfy the
syntax rules given in Rule 0. - Rule 4.
The input consists of a number of sentences consisting only of
characters p through z and N, C, D, E, and I. Each sentence is ended
by a new-line character. The collection of sentences is terminated by
the end-of-file character. If necessary, you may assume that each
sentence has at most 256 characters and at least 1 character.
The output consists of the answers YES for each well-formed sentence
and NO for each not-well-formed sentence. The answers are given in the
same order as the sentences. Each answer is followed by a new-line
character, and the list of answers is followed by an end-of-file
Cp Isz NIsz Cqpq
NO YES YES NO