answer.code:43:44: error: ‘span’ in namespace ‘std’ does not name a template type
   43 | template<typename... Ts> using Span = std::span<Ts...>;
      |                                            ^~~~
answer.code:43:39: note: ‘std::span’ is only available from C++20 onwards
   43 | template<typename... Ts> using Span = std::span<Ts...>;
      |                                       ^~~
answer.code:50:20: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   50 | constexpr auto ABS(auto x) { return (x >= 0 ? x : -x); }
      |                    ^~~~
answer.code:51:31: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   51 | constexpr auto makePair(const auto& x1, const auto& x2) { return std::make_pair(x1, x2); }
      |                               ^~~~
answer.code:51:47: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   51 | constexpr auto makePair(const auto& x1, const auto& x2) { return std::make_pair(x1, x2); }
      |                                               ^~~~
answer.code:52:30: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   52 | constexpr auto makeTup(const auto&... xs) { return std::make_tuple(xs...); }
      |                              ^~~~
answer.code:53:61: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   53 | template<typename T> constexpr auto chmin(T& x, const T& y, auto comp) -> bool { return (comp(y, x) ? (x = y, true) : false); }
      |                                                             ^~~~
answer.code:55:61: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   55 | template<typename T> constexpr auto chmax(T& x, const T& y, auto comp) -> bool { return (comp(x, y) ? (x = y, true) : false); }
      |                                                             ^~~~
answer.code:69:80: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   69 | template<typename T> constexpr auto powerMonoid(const T& x, i64 N, const T& e, auto mul) -> T
      |                                                                                ^~~~
answer.code:89:16: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   89 | auto seqConcat(auto& xs1, const auto& xs2) -> void { std::ranges::copy(xs2, std::back_inserter(xs1)); }
      |                ^~~~
answer.code:89:33: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   89 | auto seqConcat(auto& xs1, const auto& xs2) -> void { std::ranges::copy(xs2, std::back_inserter(xs1)); }
      |                                 ^~~~
answer.code: In function ‘void seqConcat(auto:35&, const auto:36&)’:
answer.code:89:59: error: ‘std::ranges’ has not been declared
   89 | auto seqConcat(auto& xs1, const auto& xs2) -> void { std::ranges::copy(xs2, std::back_inserter(xs1)); }
      |                                                           ^~~~~~
answer.code: At global scope:
answer.code:90:26: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   90 | auto seqConcatCopy(const auto& xs1, const auto& xs2)
      |                          ^~~~
answer.code:90:43: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   90 | auto seqConcatCopy(const auto& xs1, const auto& xs2)
      |                                           ^~~~
answer.code:95:22: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   95 | auto seqMinInd(const auto& xs, auto... args) -> int { return std::ranges::min_element(xs, args...) - std::ranges::begin(xs); }
      |                      ^~~~
answer.code:95:32: warning: use of ‘auto’ in parameter declaration only available with ‘-std=c++20’ or ‘-fconcepts’
   95 | auto seqMinInd(const auto& xs, auto... args) -> int { return std::ranges::min_element(xs, args...) - std::ranges::begin(xs); }
      |                                ^~~~
answer.code: In function ‘int seqMinInd(const auto:39&, auto:40 ...)’:
answer.code:95:67: error: ‘std::ranges’ has not been declared
   95 | auto seqMinInd(const auto& xs, auto... args) -> int { return std::ranges::min_element(xs, args...) - std::ranges::begin(xs); }
      |                                                                   ^~~~~~
answer.code:95:107: error: ‘std::ranges’ has not been declared
   95 | auto seqMinInd(const auto& xs, auto... args) -> int { return std::ranges::min_element(xs, args...) - std::ranges::begin(xs); }
      |                                                                                                           ^~~~~~
answer.code: At global scope:
answer.code:96:22: warning: use of ‘auto’ in parameter declara...