Language: C++

#include Mbits/stdc++.h>
using ll = long long;
int main()
{
  int X, Y, Z, K;
  std::cin >> X >> Y >> Z >> K;
  std::vector<ll> W;
  std::vector<ll> A(X), B(Y), C(Z);
  for(int i = 0; i < X; i++){std::cin >> A[i];}
  for(int i = 0; i < Y; i++){std::cin >> B[i];}
  for(int i = 0; i < Z; i++){std::cin >> C[i];}
  for(int i = 0; i < X; i++){
  	for(int j = 0; j< Y; j++){
      W.push_back(A[i]+B[j]);
    }
  }
  std::sort(W.begin(),W.end(),std::greater<ll>{});
  W.resize(K);
  std::vector<ll> V;
  for(int i = 0; i < K; i++){
    for(int j = 0; j < Z; j++){
      V.push_back(W[i]+C[j]);
    }
  }
  std::sort(V.begin(),V.end(),std::greater<ll>{});
  for(int i = 0; i < K; i++){std::cout << V[i]<<std::endl;}
  return 0;
}

Compiler output:
a.cc:1:10: error: #include expects "FILENAME" or <FILENAME>
    1 | #include Mbits/stdc++.h>
      |          ^~~~~
a.cc: In function 'int main()':
a.cc:6:8: error: 'cin' is not a member of 'std'
    6 |   std::cin >> X >> Y >> Z >> K;
      |        ^~~
a.cc:1:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
  +++ |+#include <iostream>
    1 | #include Mbits/stdc++.h>
a.cc:7:8: error: 'vector' is not a member of 'std'
    7 |   std::vector<ll> W;
      |        ^~~~~~
a.cc:1:1: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
  +++ |+#include <vector>
    1 | #include Mbits/stdc++.h>
a.cc:7:17: error: expected primary-expression before '>' token
    7 |   std::vector<ll> W;
      |                 ^
a.cc:7:19: error: 'W' was not declared in this scope
    7 |   std::vector<ll> W;
      |                   ^
a.cc:8:8: error: 'vector' is not a member of 'std'
    8 |   std::vector<ll> A(X), B(Y), C(Z);
      |        ^~~~~~
a.cc:8:8: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
a.cc:8:17: error: expected primary-expression before '>' token
    8 |   std::vector<ll> A(X), B(Y), C(Z);
      |                 ^
a.cc:8:19: error: 'A' was not declared in this scope
    8 |   std::vector<ll> A(X), B(Y), C(Z);
      |                   ^
a.cc:8:25: error: 'B' was not declared in this scope
    8 |   std::vector<ll> A(X), B(Y), C(Z);
      |                         ^
a.cc:8:31: error: 'C' was not declared in this scope
    8 |   std::vector<ll> A(X), B(Y), C(Z);
      |                               ^
a.cc:9:35: error: 'cin' is not a member of 'std'
    9 |   for(int i = 0; i < X; i++){std::cin >> A[i];}
      |                                   ^~~
a.cc:9:35: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:10:35: error: 'cin' is not a member of 'std'
   10 |   for(int i = 0; i < Y; i++){std::cin >> B[i];}
      |                                   ^~~
a.cc:10:35: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:11:35: error: 'cin' is not a member of 'std'
   11 |   for(int i = 0; i < Z; i++){std::cin >> C[i];}
      |                                   ^~~
a.cc:11:35: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:17:8: error: 'sort' is not a member of 'std'
   17 |   std::sort(W.begin(),W.end(),std::greater<ll>{});
      |        ^~~~
a.cc:17:36: error: 'greater' is not a member of 'std'
   17 |   std::sort(W.begin(),W.end(),std::greater<ll>{});
      |                                    ^~~~~~~
a.cc:17:46: error: expected primary-expression before '>' token
   17 |   std::sort(W.begin(),W.end(),std::greater<ll>{});
      |                                              ^
a.cc:17:47: error: expected primary-expression before '{' token
   17 |   std::sort(W.begin(),W.end(),std::greater<ll>{});
      |                                               ^
a.cc:19:8: error: 'vector' is not a member of 'std'
   19 |   std::vector<ll> V;
      |        ^~~~~~
a.cc:19:8: note: 'std::vector' is defined in header '<vector>'; this is probably fixable by adding '#include <vector>'
a.cc:19:17: error: expected primary-expression before '>' token
   19 |   std::vector<ll> V;
      |                 ^
a.cc:19:19: error: 'V' was not declared in this scope
   19 |   std::vector<ll> V;
      |                   ^
a.cc:25:8: error: 'sort' is not a member of 'std'
   25 |   std::sort(V.begin(),V.end(),std::greater<ll>{});
      |        ^~~~
a.cc:25:36: error: 'greater' is not a member of 'std'
   25 |   std::sort(V.begin(),V.end(),std::greater<ll>{});
      |                                    ^~~~~~~
a.cc:25:46: error: expected primary-expression before '>' token
   25 |   std::sort(V.begin(),V.end(),std::greater<ll>{});
      |                                              ^
a.cc:25:47: error: expected primary-expression before '{' token
   25 |   std::sort(V.begin(),V.end(),std::greater<ll>{});
      |                                               ^
a.cc:26:35: error: 'cout' is not a member of 'std'
   26 |   for(int i = 0; i < K; i++){std::cout << V[i]<<std::endl;}
      |                                   ^~~~
a.cc:26:35: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:26:54: error: 'endl' is not a member of 'std'
   26 |   for(int i = 0; i < K; i++){std::cout << V[i]<<std::endl;}
      |                                                      ^~~~
a.cc:1:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
  +++ |+#include <ostream>
    1 | #include Mbits/stdc++.h>