foo.cc: In function ‘int TD(std::string, int)’:
foo.cc:9:10: error: ‘ling’ was not declared in this scope; did you mean ‘long’?
    9 |     for (ling long i = 0; i < num.size(); i++)
      |          ^~~~
      |          long
foo.cc:9:27: error: ‘i’ was not declared in this scope
    9 |     for (ling long i = 0; i < num.size(); i++)
      |                           ^