/in/foo.cc: In function 'int ID(char)':
/in/foo.cc:15:13: warning: array subscript has type 'char' [-Wchar-subscripts]
   15 |     if (!id[ch])
      |             ^~
/in/foo.cc:16:12: warning: array subscript has type 'char' [-Wchar-subscripts]
   16 |         id[ch] = ++nc;
      |            ^~
/in/foo.cc:17:15: warning: array subscript has type 'char' [-Wchar-subscripts]
   17 |     return id[ch];
      |               ^~
/in/foo.cc: In function 'bool check()':
/in/foo.cc:33:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |             for (int k = 0; k < lt[i][j].size(); k++)
      |                             ~~^~~~~~~~~~~~~~~~~