/in/foo.cc: In function 'int main()':
/in/foo.cc:17:24: error: use of 'auto' in lambda parameter declaration only available with '-std=c++14' or '-std=gnu++14'
   17 |         auto dfs = [&](auto&& dfs,ull step) -> void{
      |                        ^~~~
/in/foo.cc: In lambda function:
/in/foo.cc:32:36: error: expression cannot be used as a function
   32 |                                 dfs(dfs,step + 1);
      |                                 ~~~^~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:41:12: error: no match for call to '(main()::<lambda(int&&, ull)>) (main()::<lambda(int&&, ull)>&, int)'
   41 |         dfs(dfs,0);
      |         ~~~^~~~~~~
/in/foo.cc:17:20: note: candidate: 'main()::<lambda(int&&, ull)>'
   17 |         auto dfs = [&](auto&& dfs,ull step) -> void{
      |                    ^
/in/foo.cc:17:20: note:   no known conversion for argument 1 from 'main()::<lambda(int&&, ull)>' to 'int&&'