Language: C++

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

map <string, int> memo;

int main(){
    int N;
    cin >> N;
    for (int i = 0; i < N; i++){
        string s;
        cin >> s;
        memo[s] += 1;
    }
    int maxv = 0;
    for (const auto& x : memo){
        int v = x.second;
        if (v > maxv){
            maxv = v;
        }
    }
    for (auto it = memo.begin(); it < memo.end(); it++){
        if (it ->second == maxv){
            cout << it->first << endl;
        }
    }
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:21:37: error: no match for 'operator<' (operand types are 'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' and 'std::map<std::__cxx11::basic_string<char>, int>::iterator' {aka 'std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, int>, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, int> >, std::less<std::__cxx11::basic_string<char> >, std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> > >::iterator'})
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                  ~~ ^ ~~~~~~~~~~
      |                                  |            |
      |                                  |            _Rb_tree_iterator<[...]>
      |                                  _Rb_tree_iterator<[...]>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::map<std::__cxx11::basic_string<char>, int>::iterator' {aka 'std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, int>, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, int> >, std::less<std::__cxx11::basic_string<char> >, std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::map<std::__cxx11::basic_string<char>, int>::iterator' {aka 'std::_Rb_tree<std::__cxx11::basic_string<char>, std::pair<const std::__cxx11::basic_string<char>, int>, std::_Select1st<std::pair<const std::__cxx11::basic_string<char>, int> >, std::less<std::__cxx11::basic_string<char> >, std::allocator<std::pair<const std::__cxx11::basic_string<char>, int> > >::iterator'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::pair<_T1, _T2>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::reverse_iterator<_Iterator>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::reverse_iterator<_Iterator>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::move_iterator<_IteratorL>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:21:48: note:   'std::_Rb_tree_iterator<std::pair<const std::__cxx11::basic_string<char>, int> >' is not derived from 'const std::move_iterator<_IteratorL>'
   21 |     for (auto it = memo.begin(); it < memo.end(); it++){
      |                                                ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/b