Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
int main(void){
  int n,k;
  long int num,sum=0;
  vector<long int> data(n);
  for(int i=0;i<n;i++){
    cin >> num;
    data.push_back(num);
  }
  sort(data.begin(),data.end());
  for(int i=0;i<k;i++)
    sum += data[i];
  cout << sum << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:3: error: 'vector' was not declared in this scope
    7 |   vector<long int> data(n);
      |   ^~~~~~
a.cc:7:3: 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:7:10: error: expected primary-expression before 'long'
    7 |   vector<long int> data(n);
      |          ^~~~
a.cc:9:5: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    9 |     cin >> num;
      |     ^~~
      |     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:10:5: error: 'data' was not declared in this scope; did you mean 'std::data'?
   10 |     data.push_back(num);
      |     ^~~~
      |     std::data
In file included from /usr/include/c++/14/string:53,
                 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,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/bits/range_access.h:344:5: note: 'std::data' declared here
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
a.cc:12:8: error: 'data' was not declared in this scope; did you mean 'std::data'?
   12 |   sort(data.begin(),data.end());
      |        ^~~~
      |        std::data
/usr/include/c++/14/bits/range_access.h:344:5: note: 'std::data' declared here
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
a.cc:12:3: error: 'sort' was not declared in this scope; did you mean 'std::sort'?
   12 |   sort(data.begin(),data.end());
      |   ^~~~
      |   std::sort
In file included from /usr/include/c++/14/algorithm:86,
                 from a.cc:3:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note: 'std::sort' declared here
  296 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last);
      | ^~~~
a.cc:15:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   15 |   cout << sum << 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:15:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   15 |   cout << sum << endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~