/in/foo.cc: In function 'int main()':
/in/foo.cc:9:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if (k == str.size())
      ~~^~~~~~~~~~~~~
/in/foo.cc:34:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = 1; i < str.size(); i++)
                    ~~^~~~~~~~~~~~