Language: C++

#include <bits/stdc++.h>
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define REP(i, n) FOR(i,0,n)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define IREP(i, n) IFOR(i,0,n)
#define SORT(a) sort(a.begin(), a.end())
#define REVERSE(a) reverse(a.begin(), a.end())
#define Lower_bound(v, x) distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define int long long
#define INF 1000000000000000000
using namespace std;

#define ANS(f) if(f) cout << "YES" << endl; else cout << "NO" << endl;

typedef vector<int> vec;
typedef vector<vec> mat;
typedef pair<int, int> Pii;

template<typename T>
void readv(vector<T> &a){ REP(i, a.size()) cin >> a[i]; }
void readi(vector<int> &a){ REP(i, a.size()){cin >> a[i]; a[i]--;} }
void debug(mat m){REP(i, m.size()){ REP(j, m[i].size()){ cout << m[i][j] << ","; } cout << endl; }}



signed main(){

    int N; cin >> N;
    vec A(N); readv(A);
    vector<Pii> p(N);
    set<Pii> s;
    REP(i, N){
        p[i] = Pii(A[i], i);
        s.insert(p[i]);
    }
    SORT(p);

    vector<bool> used(N, false);
    IREP(i, N){
        if(used[i]) continue;
        int x = p[i].first;
        int n = 1;
        while(n <= A[i]) n = (n << 1);
        int y = n - A;
        auto it = s.lower_bount(p[i]);
        s.erase(it);
        if(y <= x){
            auto it2 = s.lower_bount(Pii(y, -INF));
            if(it2 != s.end() && (*it2).first == y){
                ans++;
                used[(*it2).second] = true;
                s.erase(it2);
            }
        }
    }
    cout << ans;

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:45:19: error: no match for 'operator-' (operand types are 'long long int' and 'vec' {aka 'std::vector<long long int>'})
   45 |         int y = n - A;
      |                 ~ ^ ~
      |                 |   |
      |                 |   vec {aka std::vector<long long int>}
      |                 long long int
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:370:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::complex<_Tp>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/complex:379:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const _Tp&)'
  379 |     operator-(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:379:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::complex<_Tp>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/complex:388:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const _Tp&, const complex<_Tp>&)'
  388 |     operator-(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:388:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   'vec' {aka 'std::vector<long long int>'} is not derived from 'const std::complex<_Tp>'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/complex:465:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&)'
  465 |     operator-(const complex<_Tp>& __x)
      |     ^~~~~~~~
/usr/include/c++/14/complex:465:5: note:   candidate expects 1 argument, 2 provided
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   'vec' {aka 'std::vector<long long int>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   'vec' {aka 'std::vector<long long int>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const valarray<_Tp>&, const valarray<_Tp>&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::valarray<_Tp>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   mismatched types 'const std::valarray<_Tp>' and 'long long int'
   45 |         int y = n - A;
      |                     ^
/usr/include/c++/14/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__minus, _Tp>::result_type> std::operator-(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1197 | _DEFINE_BINARY_OPERATOR(-, __minus)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1197:1: note:   template argument deduction/substitution failed:
a.cc:45:21: note:   'vec' {aka 'std::vector<long long int>'} is not derived from 'const std::valarray<_Tp>'
   45 |         int y = n - A;
      |                     ^
a.cc:46:21: error: 'class std::set<std::pair<long long int, long long int> >' has no member named 'lower_bount'; did you mean 'lower_bound'?
   46 |         auto it = s.lower_bount(p[i]);
      |                     ^~~~~~~~~~~
      |                     lower_bound
a.cc:49:26: error: 'class std::set<std::pair<long long int, long long int> >' has no member named 'lower_bount'; did you mean 'lower_bound'?
   49 |             auto it2 = s.lower_bount(Pii(y, -INF));
      |                          ^~~~~~~~~~~
      |                          lower_bound
a.cc:51:17: error: 'ans' was not declared in this scope; did you mean 'abs'?
   51 |                 ans++;
      |                 ^~~
      |                 abs
a.cc:57:13: error: 'ans' was not declared in this scope; did you mean 'abs'?