/in/foo.cc: In function 'std::__cxx11::string mul(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:60:9: error: expected ';' before 'nc'
         nc[i+1]+=nc[i]/10,nc[i]%=10;//统一处理进位  
         ^~
/in/foo.cc:60:36: warning: statement has no effect [-Wunused-value]
         nc[i+1]+=nc[i]/10,nc[i]%=10;//统一处理进位  
                                    ^