Language: C++

#include <bits/stdc++.h>
int main() {
  int n;
  cin >> n;   //あられの数
  int p,y,w,g;  //色のカウンター。
  p=0;
  y=0;
  w=0;
  g=0;
  string color;
  for(int i = 0;i < n;i ++){
    cin >> color;
    if (color == "P"){
      p += 1;
    }
    if (color == "Y"){
      y += 1;
    }
    if (color == "W"){
      w +=1;
    }
    if (color == "G"){
      g += 1;
    }
  }
  if (p * y * w * g ==0){
    cout << "Three" << endl;
  }
  else{
    cout << "Four" << endl;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    4 |   cin >> n;   //あられの数
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 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: 'string' was not declared in this scope
   10 |   string color;
      |   ^~~~~~
a.cc:10:3: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:12:12: error: 'color' was not declared in this scope
   12 |     cin >> color;
      |            ^~~~~
a.cc:27:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   27 |     cout << "Three" << 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:27:24: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   27 |     cout << "Three" << endl;
      |                        ^~~~
      |                        std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:30:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   30 |     cout << "Four" << 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:30:23: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   30 |     cout << "Four" << endl;
      |                       ^~~~
      |                       std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~