/in/foo.cc: In function 'std::__cxx11::string dezero(std::__cxx11::string)':
/in/foo.cc:9:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<a.length();i++)
           ^
/in/foo.cc:13:6: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(i==a.length()) return "0";
      ^
/in/foo.cc: In function 'std::__cxx11::string multiply(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:47:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<c2.length();i++)
           ^
/in/foo.cc:52:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<c1.length();i++)
           ^
/in/foo.cc:57:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<c3.length();i++) c3.at(i)=0;
           ^
/in/foo.cc:58:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<c2.length();i++)
           ^
/in/foo.cc:60:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(j=0;j<c1.length();j++)
           ^
/in/foo.cc:65:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(k=i+j;k<c3.length()-1;k++)
             ^
/in/foo.cc:84:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=0;i<c3.length();i++)
           ^