title: long integer multiplication
body: <p>I am preparing the interview questions not for homework. There is one question about how to multiple very very long integer. Could anybody offer any source code in C++ to learn from? I am trying to reduce the gap between myself and others by learning other's solution to improve myself. </p>
  
  <p>Thanks so much!</p>
  
  <p>Sorry if you think this is not the right place to ask such questions. </p>