Language: C++

#include <bits/stdc++.h>
int main(){
  int D;
  cin >> D;
  if(D == 25){
    cout << "Christmas" << endl;
  }
  if(D == 24){
    cout << "Christmas Eve" << endl;
  }
  if(D == 23){
    cout << "Christmas Eve Eve" << endl;
  }
  if(D == 22){
    cout << "Christmas Eve Eve Eve" << endl;
    
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    4 |   cin >> D;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    6 |     cout << "Christmas" << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:6:28: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    6 |     cout << "Christmas" << endl;
      |                            ^~~~
      |                            std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:9:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 |     cout << "Christmas Eve" << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:9:32: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 |     cout << "Christmas Eve" << endl;
      |                                ^~~~
      |                                std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:12:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   12 |     cout << "Christmas Eve Eve" << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:12:36: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   12 |     cout << "Christmas Eve Eve" << endl;
      |                                    ^~~~
      |                                    std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:15:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   15 |     cout << "Christmas Eve Eve Eve" << endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:15:40: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   15 |     cout << "Christmas Eve Eve Eve" << endl;
      |                                        ^~~~
      |                                        std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:17:2: error: expected '}' at end of input
   17 | }
      |  ^
a.cc:2:11: note: to match this '{'
    2 | int main(){
      |           ^