Language: C++

#include <iostream>
using namespase std;
int main()
{
char b;
cin>>b;
if(b=='A')
{
cout<<"T"<<endl;
}
if(b=='T')
{
cout<<"A"<<endl;
}
if(b=='C')
{
cout<<"G"<<endl;
}
if(b=='G')
{
cout<<"C"<<endl;
}
return 0;
}

Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'namespase'
    2 | using namespase std;
      |       ^~~~~~~~~
a.cc: In function 'int main()':
a.cc:6:1: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 | cin>>b;
      | ^~~
      | 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:9:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 | 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:9:12: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 | cout<<"T"<<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:13:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   13 | 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:13:12: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   13 | cout<<"A"<<endl;
      |            ^~~~
      |            std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:17:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   17 | 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:17:12: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   17 | 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:21:1: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   21 | 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:21:12: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   21 | cout<<"C"<<endl;
      |            ^~~~
      |            std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~