Language: C++

#include<iostream>
#include<string>
using namespace std;
int main(){
string s,k;
  cin >> s >> k;
  if(s.size()<=k){
    cout << s >> endl;
  }
  else{
    cout << s,substr(0,k) << "..." << endl;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:14: error: no match for 'operator<=' (operand types are 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'std::string' {aka 'std::__cxx11::basic_string<char>'})
    7 |   if(s.size()<=k){
      |      ~~~~~~~~^~~
      |            |   |
      |            |   std::string {aka std::__cxx11::basic_string<char>}
      |            std::__cxx11::basic_string<char>::size_type {aka long unsigned int}
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:469:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  469 |     operator<=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:469:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/bits/stl_iterator.h:513:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  513 |     operator<=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:513:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/bits/stl_iterator.h:1704:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1704 |     operator<=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1704:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/bits/stl_iterator.h:1767:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1767 |     operator<=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1767:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
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:1064:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1064 |     operator<=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1064:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::pair<_T1, _T2>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
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:717:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  717 |     operator<=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:717:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long unsigned int'
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/string_view:724:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<=(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  724 |     operator<=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:724:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long unsigned int'
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/string_view:732:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<=(__type_identity_t<basic_string_view<_CharT, _Traits> >, basic_string_view<_CharT, _Traits>)'
  732 |     operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:732:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   'std::__cxx11::basic_string<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/bits/basic_string.h:3956:5: 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>&)'
 3956 |     operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3956:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/bits/basic_string.h:3970:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<=(const __cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 3970 |     operator<=(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3970:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
/usr/include/c++/14/bits/basic_string.h:3983:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator<=(const _CharT*, const __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 3983 |     operator<=(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.h:3983:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const _CharT*' and 'long unsigned int'
    7 |   if(s.size()<=k){
      |                ^
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:2625:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator<=(const tuple<_UTypes ...>&, const tuple<_Elements ...>&)'
 2625 |     operator<=(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/14/tuple:2625:5: note:   template argument deduction/substitution failed:
a.cc:7:16: note:   mismatched types 'const std::tuple<_UTypes ...>' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'}
    7 |   if(s.size()<=k){
      |                ^
a.cc:8:15: error: no match for 'operator>>' (operand types are 'std::basic_ostream<char>' and '<unresolved overloaded function type>')
    8 |     cout << s >> endl;
      |     ~~~~~~~~~~^~~~~~~
In file included from /usr/include/c++/14/string:55:
/usr/include/c++/14/bits/basic_string.tcc:835:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
  835 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:835:5: note:   template argument deduction/substitution failed:
a.cc:8:18: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
    8 |     cout << s >> endl;
      |                  ^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:38:
/usr/include/c++/14/cstddef:131:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator>>(byte, _IntegerType)'
  131 |     operator>>(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note:   template argument deduction/substitution failed:
a.cc:8:18: note:   couldn't deduce template parameter '_IntegerType'
    8 |     cout << s >> endl;
      |                  ^~~~
In file included from /usr/include/c++/14/istream:1109,
                 from /usr/include/c++/14/iostream:42:
/usr/include/c++/14/bits/istream.tcc:978:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&)'
  978 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note:   template argument deduction/substitution failed:
a.cc:8:18: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
    8 |     cout << s >> end