Language: C++

#include <iostream>
using std;

int main() 
{
	string hoge;
	cin >> hoge;
	if (hoge == "Cloudy") {
    	cout << "Rainy" << endl;
    } else if (hoge == "Rainy") {
    	cout << "Sunny" << endl;
    } else if (hoge == "Sunny") {
    	cout << "Cloudy" << endl;
    }
}

Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'std'
    2 | using std;
      |       ^~~
a.cc: In function 'int main()':
a.cc:6:9: error: 'string' was not declared in this scope
    6 |         string hoge;
      |         ^~~~~~
a.cc:6:9: 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:7:9: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    7 |         cin >> hoge;
      |         ^~~
      |         std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:7:16: error: 'hoge' was not declared in this scope
    7 |         cin >> hoge;
      |                ^~~~
a.cc:9:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 |         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:9:28: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 |         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:11:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |         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:11:28: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   11 |         cout << "Sunny" << endl;
      |                            ^~~~
      |                            std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:13:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   13 |         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:13:29: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 |         cout << "Cloudy" << endl;
      |                             ^~~~
      |                             std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~