Language: C++

int main(void) {
    int firstNum;
    int secondNum;
    int thirdNum;
    
    std::cin >> firstNum;
    std::cin >> secondNum;
    std::cin >> thirdNum;
    std::list<int> intList = std::list<int>();
    intList.push_back(firstNum);
    intList.push_back(secondNum);
    intList.push_back(thirdNum);
    intList.sort();
    
    // 要素を出力
    std::list<int>::iterator it = intList.begin();

    std::cout << *it << " " ;
    ++it;
    std::cout << *it << " " ;
    ++it;
    std::cout << *it << std::endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:10: error: 'cin' is not a member of 'std'
    6 |     std::cin >> firstNum;
      |          ^~~
a.cc:1:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
  +++ |+#include <iostream>
    1 | int main(void) {
a.cc:7:10: error: 'cin' is not a member of 'std'
    7 |     std::cin >> secondNum;
      |          ^~~
a.cc:7:10: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:8:10: error: 'cin' is not a member of 'std'
    8 |     std::cin >> thirdNum;
      |          ^~~
a.cc:8:10: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:9:10: error: 'list' is not a member of 'std'
    9 |     std::list<int> intList = std::list<int>();
      |          ^~~~
a.cc:1:1: note: 'std::list' is defined in header '<list>'; this is probably fixable by adding '#include <list>'
  +++ |+#include <list>
    1 | int main(void) {
a.cc:9:15: error: expected primary-expression before 'int'
    9 |     std::list<int> intList = std::list<int>();
      |               ^~~
a.cc:10:5: error: 'intList' was not declared in this scope
   10 |     intList.push_back(firstNum);
      |     ^~~~~~~
a.cc:16:10: error: 'list' is not a member of 'std'
   16 |     std::list<int>::iterator it = intList.begin();
      |          ^~~~
a.cc:16:10: note: 'std::list' is defined in header '<list>'; this is probably fixable by adding '#include <list>'
a.cc:16:15: error: expected primary-expression before 'int'
   16 |     std::list<int>::iterator it = intList.begin();
      |               ^~~
a.cc:18:10: error: 'cout' is not a member of 'std'
   18 |     std::cout << *it << " " ;
      |          ^~~~
a.cc:18:10: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:18:19: error: 'it' was not declared in this scope; did you mean 'int'?
   18 |     std::cout << *it << " " ;
      |                   ^~
      |                   int
a.cc:20:10: error: 'cout' is not a member of 'std'
   20 |     std::cout << *it << " " ;
      |          ^~~~
a.cc:20:10: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:22:10: error: 'cout' is not a member of 'std'
   22 |     std::cout << *it << std::endl;
      |          ^~~~
a.cc:22:10: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:22:30: error: 'endl' is not a member of 'std'
   22 |     std::cout << *it << 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 | int main(void) {