Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(){
    #define rep(i,n) for (int i=0,i < (int)(n);i++)

    int N;
    cin >> N;

    vector<int> a(N);
    rep(i,N){
        cin >> a.at(i);
    }

    sort(a.begin(),a.end());
    reverse(a.bein(),a,end());

    int AP=0;
    int BP=0;

    rep(i,N){
        if(i%2==0){
            AP += a.at(i);
        }
        else{
            BP += a.at(i);
        }
    }

    cout << AP - BP;
    cout << endl;
    

}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:37: error: expected ';' before '<' token
    5 |     #define rep(i,n) for (int i=0,i < (int)(n);i++)
      |                                     ^
a.cc:11:5: note: in expansion of macro 'rep'
   11 |     rep(i,N){
      |     ^~~
a.cc:5:37: error: expected primary-expression before '<' token
    5 |     #define rep(i,n) for (int i=0,i < (int)(n);i++)
      |                                     ^
a.cc:11:5: note: in expansion of macro 'rep'
   11 |     rep(i,N){
      |     ^~~
a.cc:16:15: error: 'class std::vector<int>' has no member named 'bein'; did you mean 'begin'?
   16 |     reverse(a.bein(),a,end());
      |               ^~~~
      |               begin
a.cc:16:27: error: no matching function for call to 'end()'
   16 |     reverse(a.bein(),a,end());
      |                        ~~~^~
In file included from /usr/include/c++/14/bits/algorithmfwd.h:39,
                 from /usr/include/c++/14/bits/stl_algo.h:59,
                 from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/initializer_list:99:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/c++/14/string:53,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/range_access.h:74:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/range_access.h:85:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/range_access.h:106:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:   candidate expects 1 argument, 0 provided
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/valarray:1249:5: note: candidate: 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
 1249 |     end(valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1249:5: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/valarray:1265:5: note: candidate: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
 1265 |     end(const valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1265:5: note:   candidate expects 1 argument, 0 provided
a.cc:5:37: error: expected ';' before '<' token
    5 |     #define rep(i,n) for (int i=0,i < (int)(n);i++)
      |                                     ^
a.cc:21:5: note: in expansion of macro 'rep'
   21 |     rep(i,N){
      |     ^~~
a.cc:5:37: error: expected primary-expression before '<' token
    5 |     #define rep(i,n) for (int i=0,i < (int)(n);i++)
      |                                     ^
a.cc:21:5: note: in expansion of macro 'rep'
   21 |     rep(i,N){
      |     ^~~