Language: C++

#include <iostream>
#include <string>
int main(void){
 string s;
 cin>>s;
 if(s=="Sunny"s) cout<<"Cloudy"<<endl;
 if(s=="Cloudy"s) cout<<"Rainy"<<endl;
 if(s=="Rainy"s) cout<<"Sunny"<<endl;
 return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:2: error: 'string' was not declared in this scope
    4 |  string s;
      |  ^~~~~~
a.cc:4:2: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included 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:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:5:2: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |  cin>>s;
      |  ^~~
      |  std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:7: error: 's' was not declared in this scope
    5 |  cin>>s;
      |       ^
a.cc:6:8: error: unable to find string literal operator 'operator""s' with 'const char [6]', 'long unsigned int' arguments
    6 |  if(s=="Sunny"s) cout<<"Cloudy"<<endl;
      |        ^~~~~~~~
a.cc:6:18: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    6 |  if(s=="Sunny"s) cout<<"Cloudy"<<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:6:34: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    6 |  if(s=="Sunny"s) cout<<"Cloudy"<<endl;
      |                                  ^~~~
      |                                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:7:8: error: unable to find string literal operator 'operator""s' with 'const char [7]', 'long unsigned int' arguments
    7 |  if(s=="Cloudy"s) cout<<"Rainy"<<endl;
      |        ^~~~~~~~~
a.cc:7:19: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    7 |  if(s=="Cloudy"s) cout<<"Rainy"<<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:7:34: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    7 |  if(s=="Cloudy"s) cout<<"Rainy"<<endl;
      |                                  ^~~~
      |                                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:8:8: error: unable to find string literal operator 'operator""s' with 'const char [6]', 'long unsigned int' arguments
    8 |  if(s=="Rainy"s) cout<<"Sunny"<<endl;
      |        ^~~~~~~~
a.cc:8:18: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |  if(s=="Rainy"s) cout<<"Sunny"<<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:8:33: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    8 |  if(s=="Rainy"s) cout<<"Sunny"<<endl;
      |                                 ^~~~
      |                                 std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~