answer.code:7:17: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
    7 | auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
      |                 ^~~~
answer.code:7:29: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
    7 | auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
      |                             ^~~~
answer.code:7:34: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
    7 | auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
      |                                  ^~~~
answer.code:8:17: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
    8 | auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
      |                 ^~~~
answer.code:8:24: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
    8 | auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
      |                        ^~~~
answer.code: In function ‘int main()’:
answer.code:25:24: error: missing template arguments before ‘tab’
   25 |                 vector tab(40, 0);
      |                        ^~~
answer.code:30:27: error: ‘tab’ was not declared in this scope; did you mean ‘tan’?
   30 |                         ++tab[__lg(x)];
      |                           ^~~
      |                           tan
answer.code:33:38: error: ‘tab’ was not declared in this scope; did you mean ‘tan’?
   33 |                 cout << *max_element(tab.begin(), tab.end()) << '\n';
      |                                      ^~~
      |                                      tan