Question: [General]

  Why RE?

Judge answer:

  Runtime Error may have numerous reasons such as, index array out of bounds, division by zero, allocating excessive memory.
In this online judge, using cerr and other restricted functions may cause Runtime Error too.

Question: [Problem B]

  I get Pre Error,Why?
and MS C++ supported by g++??

Judge answer:

  because your program printed extra white spaces
and for your second question, it is obvious that MS C++ is not supported by G++, you should consider including necessary libraries while submitting. For example don't forget to include string.h for memset.