Language: C++

#include <iostream>
#include <string>
#include <vector>
typedef long long ll;

int main(void)
{
  ll n;
  cin >> n;
  vector<ll> a(4, 0);
  string s;
  
  for (int i=0;i<n;i++){
    cin >> s;
    if (s == "AC"){
      a[0]++;
    }else if (s == "WA"){
      a[1]++;
    }else if (s == "TLE"){
      a[2]++;
    }else {
      a[3]++;
    }
  }
  
  cout << "AC x " << a[0] << endl;
  cout << "WA x " << a[1] << endl;
  cout << "TLE x " << a[2] << endl;
  cout << "RE x " << a[3] << endl;
  
  
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    9 |   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:10:3: error: 'vector' was not declared in this scope
   10 |   vector<ll> a(4, 0);
      |   ^~~~~~
a.cc:10:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:3:
/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:10:12: error: expected primary-expression before '>' token
   10 |   vector<ll> a(4, 0);
      |            ^
a.cc:10:14: error: 'a' was not declared in this scope
   10 |   vector<ll> a(4, 0);
      |              ^
a.cc:11:3: error: 'string' was not declared in this scope
   11 |   string s;
      |   ^~~~~~
a.cc:11:3: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included 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:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:14:12: error: 's' was not declared in this scope
   14 |     cin >> s;
      |            ^
a.cc:26:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   26 |   cout << "AC x " << a[0] << 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:26:30: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   26 |   cout << "AC x " << a[0] << endl;
      |                              ^~~~
      |                              std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~