Language: C++

#include<iostream>
#include<vector>
using namespace ltd;
int main()
{
	int n, i, B, F, R, V;
	cin >> n;	
	vector<int> b(n), f(n), r(n), v(n);
	for ( i = 0; i < n; i++ )
	{
		cin >> b[i] >> f[i] >> r[i] >> v[i];
	} 
	for ( B = 0; B < 4; B++ )
	{
		for( F = 0; F < 3; F++ )
		{
			for ( R = 0; R < 10; R++ )
			{
				cout << b[R];
			}
			cout << endl;
		}
		cout << "####################";
	}
	cout << endl;
	return 0;
}

Compiler output:
a.cc:3:17: error: 'ltd' is not a namespace-name
    3 | using namespace ltd;
      |                 ^~~
a.cc: In function 'int main()':
a.cc:7:9: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    7 |         cin >> n;
      |         ^~~
      |         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:8:9: error: 'vector' was not declared in this scope
    8 |         vector<int> b(n), f(n), r(n), v(n);
      |         ^~~~~~
a.cc:8:9: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:2:
/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:8:16: error: expected primary-expression before 'int'
    8 |         vector<int> b(n), f(n), r(n), v(n);
      |                ^~~
a.cc:11:24: error: 'b' was not declared in this scope
   11 |                 cin >> b[i] >> f[i] >> r[i] >> v[i];
      |                        ^
a.cc:11:32: error: 'f' was not declared in this scope
   11 |                 cin >> b[i] >> f[i] >> r[i] >> v[i];
      |                                ^
a.cc:11:40: error: 'r' was not declared in this scope
   11 |                 cin >> b[i] >> f[i] >> r[i] >> v[i];
      |                                        ^
a.cc:11:48: error: 'v' was not declared in this scope
   11 |                 cin >> b[i] >> f[i] >> r[i] >> v[i];
      |                                                ^
a.cc:19:33: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   19 |                                 cout << b[R];
      |                                 ^~~~
      |                                 std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:19:41: error: 'b' was not declared in this scope
   19 |                                 cout << b[R];
      |                                         ^
a.cc:21:25: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   21 |                         cout << 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:21:33: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   21 |                         cout << 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:23:17: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   23 |                 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:25:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   25 |         cout << 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:25:17: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   25 |         cout << endl;
      |                 ^~~~
      |                 std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~