/in/foo.cc: In constructor 'Change::Change(std::vector<char>&)':
/in/foo.cc:19:6: warning: unused variable 'num' [-Wunused-variable]
  int num = vec.size();
      ^~~
/in/foo.cc: In member function 'void Change::check()':
/in/foo.cc:30:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<store.size(); i++) {
                  ~^~~~~~~~~~~~~
/in/foo.cc:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<present.size(); i++) {
                  ~^~~~~~~~~~~~~~~
/in/foo.cc: In member function 'bool Change::count(int)':
/in/foo.cc:88:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^