In file included from /usr/include/c++/13/unordered_map:37,
                 from answer.code:3:
/usr/include/c++/13/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
   32 | #error This file requires compiler and library support \
      |  ^~~~~
answer.code: In function ‘int main()’:
answer.code:15:10: error: ‘sort’ is not a member of ‘std’
   15 |     std::sort(b.begin(), b.end());
      |          ^~~~
answer.code:20:35: error: ‘>>’ should be ‘> >’ within a nested template argument list
   20 |     std::vector<std::pair<int, int>> result;
      |                                   ^~
      |                                   > >
answer.code:29:13: error: ‘exit’ was not declared in this scope
   29 |             exit(0);
      |             ^~~~
answer.code:4:1: note: ‘exit’ is defined in header ‘<cstdlib>’; did you forget to ‘#include <cstdlib>’?
    3 | #include <unordered_map>
  +++ |+#include <cstdlib>
    4 | 
answer.code:35:10: error: ‘unordered_map’ is not a member of ‘std’
   35 |     std::unordered_map<int, int> index;
      |          ^~~~~~~~~~~~~
answer.code:35:10: note: ‘std::unordered_map’ is only available from C++11 onwards
answer.code:35:24: error: expected primary-expression before ‘int’
   35 |     std::unordered_map<int, int> index;
      |                        ^~~
answer.code:38:19: error: ‘index’ was not declared in this scope; did you mean ‘idx’?
   38 |         int idx = index[j];
      |                   ^~~~~
      |                   idx
answer.code:46:22: error: ISO C++ forbids declaration of ‘tup’ with no type [-fpermissive]
   46 |     for (const auto& tup : result) {
      |                      ^~~
answer.code:46:28: warning: range-based ‘for’ loops only available with ‘-std=c++11’ or ‘-std=gnu++11’ [-Wc++11-extensions]
   46 |     for (const auto& tup : result) {
      |                            ^~~~~~
answer.code:46:28: error: forming reference to reference type ‘std::vector<std::pair<int, int> >&’
answer.code:47:21: error: request for member ‘first’ in ‘tup’, which is of non-class type ‘const int’
   47 |         int i = tup.first;
      |                     ^~~~~
answer.code:48:21: error: request for member ‘second’ in ‘tup’, which is of non-class type ‘const int’
   48 |         int j = tup.second;
      |                     ^~~~~~
answer.code:49:22: error: no matching function for call to ‘find(std::vector<int>::iterator, std::vector<int>::iterator, int&)’
   49 |         if (std::find(ret_.begin(), ret_.end(), i) == ret_.end() && std::find(ret_.begin(), ret_.end(), j) == ret_.end()) {
      |             ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/13/bits/locale_facets.h:48,
                 from /usr/include/c++/13/bits/basic_ios.h:37,
                 from /usr/include/c++/13/ios:46,
                 from /usr/include/c++/13/ostream:40,
                 from /usr/include/c++/13/iostream:41,
                 from answer.code:1:
/usr/include/c++/13/bits/streambuf_iterator.h:435:5: note: candidate: ‘template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)’
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/13/bits/streambuf_iterator.h:435:5: note:   template argument deduction/substitution failed:
answer.code:49:22: note:   ‘__gnu_cxx::__normal_iterator<int*, std::vector<int> >’ is not derived from ‘std::istreambuf_iterator<_CharT>’
   49 |         if (std::find(ret_.begin(), ret_.end(), i) == ret_.end() && std::find(ret_.begin(), ret_.end(), j) == ret_.end()) {
      |             ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
answer.code:49:78: error: no matching function for call to ‘find(std::vector<int>::iterator, std::vector<int>::iterator, int&)’
   49 |         if (std::find(ret_.begin(), ret_.end(), i) == ret_.end() && std::find(ret_.begin(), ret_.end(), j) == ret_.end()) {
      |                                                                     ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/13/bits/streambuf_iterator.h:435:5: note: candidate: ‘template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)’
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/13/bits/streambuf_iterator.h:435:5: note:   template argument deduction/substitution failed:
answer.code:49:78: note:   ‘__gnu_cxx::__normal_iterator<int*, std::vector<int> >’ is not derived from ‘std::istreambuf_iterator<_CharT>’
   49 |         if (std::find(ret_.begin(), ret_.end(), i) == ret_.end() && std::find(ret_.begin(), ret...