Language: C++

#import<iostream>
main(){int n,c,i,a[1<<17]={};for(std::cin>>n;n--;){std::cin>>i;c+=!a[i]++;}for(i=1<<17;i--;)n^=~a[i]&1;std::cout<<n&1?c-1:c;}

Compiler output:
a.cc:1:2: warning: #import is a deprecated GCC extension [-Wdeprecated]
    1 | #import<iostream>
      |  ^~~~~~
a.cc:2:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
    2 | main(){int n,c,i,a[1<<17]={};for(std::cin>>n;n--;){std::cin>>i;c+=!a[i]++;}for(i=1<<17;i--;)n^=~a[i]&1;std::cout<<n&1?c-1:c;}
      | ^~~~
a.cc: In function 'int main()':
a.cc:2:116: error: no match for 'operator&' (operand types are 'std::basic_ostream<char>' and 'int')
    2 | main(){int n,c,i,a[1<<17]={};for(std::cin>>n;n--;){std::cin>>i;c+=!a[i]++;}for(i=1<<17;i--;)n^=~a[i]&1;std::cout<<n&1?c-1:c;}
      |                                                                                                        ~~~~~~~~~~~~^~
      |                                                                                                                 |   |
      |                                                                                                                 |   int
      |                                                                                                                 std::basic_ostream<char>
a.cc:2:116: note: candidate: 'operator&(int, int)' (built-in)
    2 | main(){int n,c,i,a[1<<17]={};for(std::cin>>n;n--;){std::cin>>i;c+=!a[i]++;}for(i=1<<17;i--;)n^=~a[i]&1;std::cout<<n&1?c-1:c;}
      |                                                                                                        ~~~~~~~~~~~~^~
a.cc:2:116: note:   no known conversion for argument 1 from 'std::basic_ostream<char>' to 'int'
In file included from /usr/include/c++/14/bits/memory_resource.h:38,
                 from /usr/include/c++/14/string:68,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/cstddef:141:3: note: candidate: 'constexpr std::byte std::operator&(byte, byte)'
  141 |   operator&(byte __l, byte __r) noexcept
      |   ^~~~~~~~
/usr/include/c++/14/cstddef:141:18: note:   no known conversion for argument 1 from 'std::basic_ostream<char>' to 'std::byte'
  141 |   operator&(byte __l, byte __r) noexcept
      |             ~~~~~^~~
/usr/include/c++/14/bits/ios_base.h:84:3: note: candidate: 'constexpr std::_Ios_Fmtflags std::operator&(_Ios_Fmtflags, _Ios_Fmtflags)'
   84 |   operator&(_Ios_Fmtflags __a, _Ios_Fmtflags __b) _GLIBCXX_NOTHROW
      |   ^~~~~~~~
/usr/include/c++/14/bits/ios_base.h:84:27: note:   no known conversion for argument 1 from 'std::basic_ostream<char>' to 'std::_Ios_Fmtflags'
   84 |   operator&(_Ios_Fmtflags __a, _Ios_Fmtflags __b) _GLIBCXX_NOTHROW
      |             ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/ios_base.h:134:3: note: candidate: 'constexpr std::_Ios_Openmode std::operator&(_Ios_Openmode, _Ios_Openmode)'
  134 |   operator&(_Ios_Openmode __a, _Ios_Openmode __b) _GLIBCXX_NOTHROW
      |   ^~~~~~~~
/usr/include/c++/14/bits/ios_base.h:134:27: note:   no known conversion for argument 1 from 'std::basic_ostream<char>' to 'std::_Ios_Openmode'
  134 |   operator&(_Ios_Openmode __a, _Ios_Openmode __b) _GLIBCXX_NOTHROW
      |             ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/ios_base.h:181:3: note: candidate: 'constexpr std::_Ios_Iostate std::operator&(_Ios_Iostate, _Ios_Iostate)'
  181 |   operator&(_Ios_Iostate __a, _Ios_Iostate __b) _GLIBCXX_NOTHROW
      |   ^~~~~~~~
/usr/include/c++/14/bits/ios_base.h:181:26: note:   no known conversion for argument 1 from 'std::basic_ostream<char>' to 'std::_Ios_Iostate'
  181 |   operator&(_Ios_Iostate __a, _Ios_Iostate __b) _GLIBCXX_NOTHROW
      |             ~~~~~~~~~~~~~^~~