Language: C++

#include<iostream>
uding namespace std;
int main(){
  int a;
  cin>>a;
  if(a=="G"){
    cout<<"C"<<endl;
  }
  if(a=="C"){
    cout<<"G"<<endl;
  }
  if(a=="A"){
    cout<<"T"<<endl;
  }
  if(a=="T"){
    cout<<"A"<<endl;
  }
}
    

Compiler output:
a.cc:2:1: error: 'uding' does not name a type
    2 | uding namespace std;
      | ^~~~~
a.cc: In function 'int main()':
a.cc:5:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   cin>>a;
      |   ^~~
      |   std::cin
In file included 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:6:7: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
    6 |   if(a=="G"){
      |      ~^~~~~
a.cc:7:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    7 |     cout<<"C"<<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:7:16: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    7 |     cout<<"C"<<endl;
      |                ^~~~
      |                std::endl
In file included from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:9:7: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
    9 |   if(a=="C"){
      |      ~^~~~~
a.cc:10:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   10 |     cout<<"G"<<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:10:16: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   10 |     cout<<"G"<<endl;
      |                ^~~~
      |                std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:12:7: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
   12 |   if(a=="A"){
      |      ~^~~~~
a.cc:13:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   13 |     cout<<"T"<<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:13:16: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 |     cout<<"T"<<endl;
      |                ^~~~
      |                std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:15:7: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
   15 |   if(a=="T"){
      |      ~^~~~~
a.cc:16:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   16 |     cout<<"A"<<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:16:16: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   16 |     cout<<"A"<<endl;
      |                ^~~~
      |                std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~