Language: C++

#include <bits/stdc++.h>
#include <vector>
#include <numeric>
#define PI 3.14159265358979323846
#define MAXINF (1e18L)
#define INF (1e9L)
#define EPS (1e-9)
#define MOD ((ll)(1e9+7))
#define REP(i, n) for(int i=0;i<int(n);++i)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define RREP(i, n) for(int i=int(n)-1;i>=0;--i)
#define ALL(v) v.begin(),v.end()
#define FIND(v,x) (binary_search(ALL(v),(x)))
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v));reverse(ALL(v))
#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl
#define Yes(n) cout<<((n)?"Yes":"No")<<endl
#define YES(n) cout<<((n)?"YES":"NO")<<endl
#define pb push_back
#define fi first
#define se second
using namespace std;
template<class A>void pr(A a){cout << (a) << endl;}
template<class A,class B>void pr(A a,B b){cout << a << " "  ;pr(b);}
template<class A,class B,class C>void pr(A a,B b,C c){cout << a << " " ;pr(b,c);}
template<class A,class B,class C,class D>void pr(A a,B b,C c,D d){cout << a << " " ;pr(b,c,d);}
template<class T> inline bool chmin(T& a, T b){return a>b ? a=b, true : false;}
template<class T> inline bool chmax(T& a, T b){return a<b ? a=b, true : false;}
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll,ll> pll;

int main(void)
{
    int N;
    cin >> N;
    map<int, int> m;
    REP(i, N){
        int a;
        cin >> a;
        m[a]++;
    }
    int ans = 0;
    for(auto&& i: m){
        if(i&1){
            ans++;
        }
    }
    pr(ans);
}

Compiler output:
a.cc: In function 'int main()':
a.cc:46:13: error: no match for 'operator&' (operand types are 'std::pair<const int, int>' and 'int')
   46 |         if(i&1){
      |            ~^~
      |            | |
      |            | int
      |            std::pair<const int, int>
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bitset:1557:5: note: candidate: 'template<long unsigned int _Nb> std::bitset<_Nb> std::operator&(const bitset<_Nb>&, const bitset<_Nb>&)'
 1557 |     operator&(const bitset<_Nb>& __x, const bitset<_Nb>& __y) _GLIBCXX_NOEXCEPT
      |     ^~~~~~~~
/usr/include/c++/14/bitset:1557:5: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   'std::pair<const int, int>' is not derived from 'const std::bitset<_Nb>'
   46 |         if(i&1){
      |              ^
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:411:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__bitwise_and, typename _Dom1::value_type>::result_type> std::operator&(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  411 |     _DEFINE_EXPR_BINARY_OPERATOR(&, struct std::__bitwise_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:411:5: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   'std::pair<const int, int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/bits/valarray_after.h:411:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__bitwise_and, typename _Dom1::value_type>::result_type> std::operator&(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  411 |     _DEFINE_EXPR_BINARY_OPERATOR(&, struct std::__bitwise_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:411:5: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   'std::pair<const int, int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/bits/valarray_after.h:411:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__bitwise_and, typename _Dom1::value_type>::result_type> std::operator&(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  411 |     _DEFINE_EXPR_BINARY_OPERATOR(&, struct std::__bitwise_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:411:5: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/bits/valarray_after.h:411:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__bitwise_and, typename _Dom1::value_type>::result_type> std::operator&(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  411 |     _DEFINE_EXPR_BINARY_OPERATOR(&, struct std::__bitwise_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:411:5: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   'std::pair<const int, int>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/bits/valarray_after.h:411:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__bitwise_and, typename _Dom1::value_type>::result_type> std::operator&(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  411 |     _DEFINE_EXPR_BINARY_OPERATOR(&, struct std::__bitwise_and)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:411:5: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/valarray:1202:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__bitwise_and, _Tp>::result_type> std::operator&(const valarray<_Tp>&, const valarray<_Tp>&)'
 1202 | _DEFINE_BINARY_OPERATOR(&, __bitwise_and)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1202:1: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   'std::pair<const int, int>' is not derived from 'const std::valarray<_Tp>'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/valarray:1202:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__bitwise_and, _Tp>::result_type> std::operator&(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1202 | _DEFINE_BINARY_OPERATOR(&, __bitwise_and)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1202:1: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   'std::pair<const int, int>' is not derived from 'const std::valarray<_Tp>'
   46 |         if(i&1){
      |              ^
/usr/include/c++/14/valarray:1202:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__bitwise_and, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__bitwise_and, _Tp>::result_type> std::operator&(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1202 | _DEFINE_BINARY_OPERATOR(&, __bitwise_and)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1202:1: note:   template argument deduction/substitution failed:
a.cc:46:14: note:   mismatched types 'const std::valarray<_Tp>' and 'int'
   46 |         if(i&1){
      |              ^
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:41:
/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::pair<const int, int>' to 'std::byte'
  141 |   operator&(byte __l, byte __r) noexcept
      |             ~~~~~^~~
In file included from /usr/include/c++/14/streambuf:43,
                 from /usr/include/c++/14/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/14/iterator:66,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:54:
/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::pair<const int, int>' 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::pair<const int, int>' 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::pair<const int, int>' to 'std::_Ios_Iostate'
  181 |   operator&(_Ios_Iostate __a, _Ios_Iostate __b) _GLIBCXX_NOTHROW
      |             ~~~~~~~~~~~~~^~~
In file included from /usr/include/c++/14/bits/shared_ptr_atomic.h:33,
                 from /usr/include/c++/14/memory:81,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:56:
/usr/include/c++/14/bits/atomic_base.h:109:3: note: candidate: 'constexpr std::memory_order std::operator&(memory_order, __memory_order_modifier)'
  109 |   operator&(memory_order __m, __memory_order_modifier __mod) noexcept
      |   ^~~~~~~~
/usr/include/c++/14/bits/atomic_base.h:109:26: note:   no known conversion for argument 1 from 'std::pair<const int, int>' to 'std::memory_order'
  109 |   operator&(memory_order __m, __memory_order_modifier __mod) noexcept
      |             ~~~~~~~~~~~~~^~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:176:
/usr/include/c++/14/future:156:20: note: candidate: 'constexpr std::launch std::operator&(launch, launch)'
  156 |   constexpr launch operator&(launch __x, launch __y) noexcept
      |                    ^~~~~~~~
/usr/include/c++/14/future:156:37: note:   no known conversion for argument 1 from 'std::pair<const int, int>' to 'std::launch'
  156 |   constexpr launch operator&(launch __x, launch __y) noexcept
      |                              ~~~~~~~^~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:198:
/usr/include/c++/14/charconv:632:3: