/in/foo.cc: In function 'void dfs(int, int, std::string)':
/in/foo.cc:14:28: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   14 |         if(s.length() - idx<k-cnt) return;
      |            ~~~~~~~~~~~~~~~~^~~~~~
/in/foo.cc:16:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |         if(idx==s.length())
      |            ~~~^~~~~~~~~~~~
/in/foo.cc:20:29: warning: unused variable 'i' [-Wunused-variable]
   20 |                         int i=0;
      |                             ^