In file included from /usr/include/c++/11/unordered_set:35,
                 from answer.code:6:
/usr/include/c++/11/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 countIdealCompetitions(std::vector<std::__cxx11::basic_string<char> >&)’:
answer.code:12:5: error: ‘unordered_set’ was not declared in this scope
   12 |     unordered_set<string> uniqueSets;
      |     ^~~~~~~~~~~~~
answer.code:12:5: note: ‘std::unordered_set’ is only available from C++11 onwards
answer.code:12:25: error: expected primary-expression before ‘>’ token
   12 |     unordered_set<string> uniqueSets;
      |                         ^
answer.code:12:27: error: ‘uniqueSets’ was not declared in this scope
   12 |     unordered_set<string> uniqueSets;
      |                           ^~~~~~~~~~