Problem Statement  
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Taro shows a magic trick to Hanako. Taro: Hello Hanako. I'll show you a magic trick. Please imagine a positive integer less than or equal to 16. Hanako: OK. I imagined it. Taro: (Taro shows card 1 to Hanako.) Does this card contain your number? Hanako: Yes. Taro: (Taro shows card 2 to Hanako.) Does this card contain your number? Hanako: No. Taro: (Taro shows card 3 to Hanako.) Does this card contain your number? Hanako: Yes. Taro: (Taro shows card 4 to Hanako.) Does this card contain your number? Hanako: Yes. Taro: Your number is 5! (Card 1 contains 1, 2, 3, 4, 5, 6, 7 and 8. Card 2 contains 1, 2, 3, 4, 9, 10, 11 and 12. Card 3 contains 1, 2, 5, 6, 9, 10, 13 and 14. Card 4 contains 1, 3, 5, 7, 9, 11, 13 and 15.) Your task is to write a program that simulates this magic trick. You are given Hanako's answers in the String answer. The ith character is 'Y' if she answered "yes" to the ith question, and 'N' if she answered "no" to the ith question. Return the integer Hanako imagined.  
Definition  
 
Constraints  
  answer will contain exactly 4 characters.  
  Each character in answer will be 'Y' or 'N'.  
Examples  
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