/in/foo.cc: In function 'int main()':
/in/foo.cc:8:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < s.length()-1; i++)
                  ~~^~~~~~~~~~~~~~
/in/foo.cc:13:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 1; i < m.length(); i++)
                  ~~^~~~~~~~~~~~
/in/foo.cc:6:6: warning: unused variable 'n' [-Wunused-variable]
  int n = 0, b = 0;
      ^
/in/foo.cc:6:13: warning: unused variable 'b' [-Wunused-variable]
  int n = 0, b = 0;
             ^