Language: C++

#include<iostream>
using namespace std;

int main(){
  string s1,s2,s3;
  cin >> s1 >> s2 >> s3;
  cout << transform(s1.cbegin(0)),s1.cend(1),s1.begin(0),toupper)
    << transform(s2.cbegin(0)),s2.cend(1),s2.begin(0),toupper)
    << transform(s3.cbegin(0)),s3.cend(1),s3.begin(0),toupper)
    << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:30: error: no matching function for call to 'std::__cxx11::basic_string<char>::cbegin(int)'
    7 |   cout << transform(s1.cbegin(0)),s1.cend(1),s1.begin(0),toupper)
      |                     ~~~~~~~~~^~~
In file included from /usr/include/c++/14/string:54,
                 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/basic_string.h:1037:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::const_iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::cbegin() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; const_iterator = std::__cxx11::basic_string<char>::const_iterator]'
 1037 |       cbegin() const noexcept
      |       ^~~~~~
/usr/include/c++/14/bits/basic_string.h:1037:7: note:   candidate expects 0 arguments, 1 provided
a.cc:7:11: error: 'transform' was not declared in this scope
    7 |   cout << transform(s1.cbegin(0)),s1.cend(1),s1.begin(0),toupper)
      |           ^~~~~~~~~
a.cc:7:42: error: no matching function for call to 'std::__cxx11::basic_string<char>::cend(int)'
    7 |   cout << transform(s1.cbegin(0)),s1.cend(1),s1.begin(0),toupper)
      |                                   ~~~~~~~^~~
/usr/include/c++/14/bits/basic_string.h:1046:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::const_iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::cend() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; const_iterator = std::__cxx11::basic_string<char>::const_iterator]'
 1046 |       cend() const noexcept
      |       ^~~~
/usr/include/c++/14/bits/basic_string.h:1046:7: note:   candidate expects 0 arguments, 1 provided
a.cc:7:54: error: no matching function for call to 'std::__cxx11::basic_string<char>::begin(int)'
    7 |   cout << transform(s1.cbegin(0)),s1.cend(1),s1.begin(0),toupper)
      |                                              ~~~~~~~~^~~
/usr/include/c++/14/bits/basic_string.h:960:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::begin() [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; iterator = std::__cxx11::basic_string<char>::iterator]'
  960 |       begin() _GLIBCXX_NOEXCEPT
      |       ^~~~~
/usr/include/c++/14/bits/basic_string.h:960:7: note:   candidate expects 0 arguments, 1 provided
/usr/include/c++/14/bits/basic_string.h:969:7: note: candidate: 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::const_iterator std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::begin() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; const_iterator = std::__cxx11::basic_string<char>::const_iterator]'
  969 |       begin() const _GLIBCXX_NOEXCEPT
      |       ^~~~~
/usr/include/c++/14/bits/basic_string.h:969:7: note:   candidate expects 0 arguments, 1 provided