questionCorrection

A system of Online Q&A needs user’s questions to be standardized.

A standardized question must satisfy this following rules:

• Common rules: Question only contains letter (a-zA-Z), number, comma, space, question mark characters. Other character should be replaced by space.
• Space rules:
  No space in the head of sentence, no space in the end of sentence. No more than 1 space between the words in 1 sentence.
  There must be a letter or number after a space.
• Comma rules:
  There must be a letter or number before a comma and only 1 space after a comma.
• Uppercase / lowercase rules:
  The first letter in a sentence must be an uppercase
  All of other letter in a sentence must be lowercase except for the first letter.
• Question mark rules:
  There is alway has one question mark at the end of sentence.
  There must be 1 letter before a question mark.
  If the question mark appears in the middle of sentence then replace the question mark by a space.

Input/Output:

• [execution time limit] 0.5 seconds (cpp)
• [input] string x
  string of input letters which contains atleast one letter (a-zA-Z)
• [output] string
  String of letters which are standardized according to the rules of system