Language: C++

#include<bits/stdc++.h>

int main() {
  int H,W;
  cin >> H,W >> endl;
  H += 2
  
  for (int i = 0;i < H;i++) {
    cout << "#" << endl;
  }
  cout << "#";
  vector <string> A(N);
  for (int i =0;i < N;i++) {
    cin >> A.at(i) >> endl;
    cout << A.at(i);
  }
  cout << "#" << endl;
   cout << "#";
  vector <string> B(N);
  for (int i =0;i < N;i++) {
    cin >> B.at(i) >> endl;
    cout << B.at(i);
  }
  cout << "#" << endl;
    for (int i = 0;i < H;i++) {
    cout << "#" << endl;
  }
}
  
  
  
  
 

Compiler output:
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 >> H,W >> endl;
      |   ^~~
      |   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:5:17: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    5 |   cin >> H,W >> 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:6:9: error: expected ';' before 'for'
    6 |   H += 2
      |         ^
      |         ;
    7 | 
    8 |   for (int i = 0;i < H;i++) {
      |   ~~~    
a.cc:8:18: error: 'i' was not declared in this scope
    8 |   for (int i = 0;i < H;i++) {
      |                  ^
a.cc:11:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |   cout << "#";
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:12:3: error: 'vector' was not declared in this scope
   12 |   vector <string> A(N);
      |   ^~~~~~
a.cc:12:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:12:11: error: 'string' was not declared in this scope
   12 |   vector <string> A(N);
      |           ^~~~~~
a.cc:12:11: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:12:21: error: 'N' was not declared in this scope
   12 |   vector <string> A(N);
      |                     ^
a.cc:12:19: error: 'A' was not declared in this scope
   12 |   vector <string> A(N);
      |                   ^
a.cc:19:19: error: 'B' was not declared in this scope
   19 |   vector <string> B(N);
      |                   ^