Language: C++

#include<iostream>
#include <stdio.h>
#include<string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <cstdint>
#include <queue> 
#include <map>
#include <set>
#define MOD 1000000007
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n)  FOR(i,0,n)
#define dump(x)  cout << #x << " = " << (x) << endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
typedef long long ll;
using namespace std;

int main(){

  int a,b,n;
  cin >> n >> a >> b;
  
  int ans = 0;
  FOR(i,1,n+1){
    int sum = 0;
    if(i < 10) sum += i;
    else if(i < 100) sum += (i/10) + (i%10);
    else if(i < 1000) sum += (i/100) +((i/10)%10) + i%10;
    else if(i < 10000) sum += (i/1000) + ((i/100)%10) +((i/10)%10) + i%10;
    else sum = 1;
    
    if(sum >= a && sum <= b) ans += i;
    
  }
  
  cout << ans < endl;

 return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:37:15: error: no match for 'operator<' (operand types are 'std::basic_ostream<char>' and '<unresolved overloaded function type>')
   37 |   cout << ans < endl;
      |   ~~~~~~~~~~~~^~~~~~
In file included from /usr/include/c++/14/string:48,
                 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/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:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   37 |   cout << ans < endl;
      |                 ^~~~
/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:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   37 |   cout << ans < endl;
      |                 ^~~~
/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:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   37 |   cout << ans < endl;
      |                 ^~~~
/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:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string: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:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::pair<_T1, _T2>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   37 |   cout << ans < endl;
      |                 ^~~~
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  680 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:680:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   37 |   cout << ans < endl;
      |                 ^~~~
/usr/include/c++/14/string_view:688:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  688 |     operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:688:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   couldn't deduce template parameter '_CharT'
   37 |   cout << ans < endl;
      |                 ^~~~
/usr/include/c++/14/bits/basic_string.h:3874:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3874 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3874:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   37 |   cout << ans < endl;
      |                 ^~~~
/usr/include/c++/14/bits/basic_string.h:3888:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3888 |     operator<(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3888:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   37 |   cout << ans < endl;
      |                 ^~~~
/usr/include/c++/14/bits/basic_string.h:3901:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3901 |     operator<(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3901:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   mismatched types 'const _CharT*' and 'std::basic_ostream<char>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2600:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator<(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2600 |     operator<(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2600:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::tuple<_UTypes ...>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:6:
/usr/include/c++/14/bits/stl_vector.h:2089:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
 2089 |     operator<(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:2089:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::vector<_Tp, _Alloc>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/deque:66,
                 from /usr/include/c++/14/queue:62,
                 from a.cc:8:
/usr/include/c++/14/bits/stl_deque.h:2334:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator<(const deque<_Tp, _Alloc>&, const deque<_Tp, _Alloc>&)'
 2334 |     operator<(const deque<_Tp, _Alloc>& __x, const deque<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_deque.h:2334:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::deque<_Tp, _Alloc>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/queue:66:
/usr/include/c++/14/bits/stl_queue.h:397:5: note: candidate: 'template<class _Tp, class _Seq> bool std::operator<(const queue<_Tp, _Seq>&, const queue<_Tp, _Seq>&)'
  397 |     operator<(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_queue.h:397:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::queue<_Tp, _Seq>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/map:63,
                 from a.cc:9:
/usr/include/c++/14/bits/stl_map.h:1550:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const map<_Key, _Tp, _Compare, _Allocator>&, const map<_Key, _Tp, _Compare, _Allocator>&)'
 1550 |     operator<(const map<_Key, _Tp, _Compare, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_map.h:1550:5: note:   template argument deduction/substitution failed:
a.cc:37:17: note:   'std::basic_ostream<char>' is not derived from 'const std::map<_Key, _Tp, _Compare, _Allocator>'
   37 |   cout << ans < endl;
      |                 ^~~~
In file included from /usr/include/c++/14/map:6