Language: C++

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace AOJ
{
    class Program
    {
        static void Main(string[] args)
        {
            string s;
            while ((s = Console.ReadLine()) != null)
            {
                var list = s.Split(',').Select(int.Parse).ToList();
                list.Sort();
                var dict = new Dictionary<int, int>();
                foreach (var v in list)
                {
                    if (dict.ContainsKey(v))
                    {
                        var i = dict[v] + 1;
                        dict.Remove(v); dict.Add(v, i);
                    }
                    else
                    {
                        dict.Add(v, 1);
                    }
                }
                bool isStraight = true;
                for (int i = list[0]; i < list[0] + 5; i++)
                {
                    if (list[i - list[0]] != i) { isStraight = false; break; }
                }
                if (list[0] == 1)
                {
                    isStraight = true;
                    for (int i = 0; i < 4; i++)
                    {
                        if (list[i+1] != 10+i) { isStraight = false; break; }
                    }
                }

                bool isFour = false;
                bool isThree = false;
                int Pairs = 0;

                var lk = dict.Keys;
                foreach (var v in lk)
                {
                    isFour |= dict[v] == 4;
                    isThree |= dict[v] == 3;
                    Pairs += dict[v] == 2 ? 1 : 0;
                }

                string result = "null";

                if (isFour) result = "four card";
                else if (isThree && Pairs > 0) result = "full house";
                else if (isStraight) result = "straight";
                else if (isThree) result = "three card";
                else if (Pairs == 2) result = "two pairs";
                else if (Pairs > 0) result = "one pair";

                Console.WriteLine(result);
            }
        }
    }
}

Compiler output:
a.cc:1:7: error: expected nested-name-specifier before 'System'
    1 | using System;
      |       ^~~~~~
a.cc:2:7: error: expected nested-name-specifier before 'System'
    2 | using System.Collections.Generic;
      |       ^~~~~~
a.cc:3:7: error: expected nested-name-specifier before 'System'
    3 | using System.Linq;
      |       ^~~~~~
a.cc:4:7: error: expected nested-name-specifier before 'System'
    4 | using System.Text;
      |       ^~~~~~
a.cc:10:26: error: 'string' has not been declared
   10 |         static void Main(string[] args)
      |                          ^~~~~~
a.cc:10:35: error: expected ',' or '...' before 'args'
   10 |         static void Main(string[] args)
      |                                   ^~~~
a.cc:68:6: error: expected ';' after class definition
   68 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void AOJ::Program::Main(int*)':
a.cc:12:13: error: 'string' was not declared in this scope
   12 |             string s;
      |             ^~~~~~
a.cc:13:21: error: 's' was not declared in this scope
   13 |             while ((s = Console.ReadLine()) != null)
      |                     ^
a.cc:13:25: error: 'Console' was not declared in this scope
   13 |             while ((s = Console.ReadLine()) != null)
      |                         ^~~~~~~
a.cc:13:48: error: 'null' was not declared in this scope
   13 |             while ((s = Console.ReadLine()) != null)
      |                                                ^~~~
a.cc:15:17: error: 'var' was not declared in this scope
   15 |                 var list = s.Split(',').Select(int.Parse).ToList();
      |                 ^~~
a.cc:16:17: error: 'list' was not declared in this scope
   16 |                 list.Sort();
      |                 ^~~~
a.cc:17:21: error: expected ';' before 'dict'
   17 |                 var dict = new Dictionary<int, int>();
      |                     ^~~~
a.cc:18:30: error: expected ')' before 'v'
   18 |                 foreach (var v in list)
      |                              ^
a.cc:18:25: note: to match this '('
   18 |                 foreach (var v in list)
      |                         ^
a.cc:18:17: error: 'foreach' was not declared in this scope
   18 |                 foreach (var v in list)
      |                 ^~~~~~~
a.cc:48:21: error: expected ';' before 'lk'
   48 |                 var lk = dict.Keys;
      |                     ^~
a.cc:49:30: error: expected ')' before 'v'
   49 |                 foreach (var v in lk)
      |                              ^
a.cc:49:25: note: to match this '('
   49 |                 foreach (var v in lk)
      |                         ^
a.cc:56:24: error: expected ';' before 'result'
   56 |                 string result = "null";
      |                        ^~~~~~
a.cc:58:29: error: 'result' was not declared in this scope
   58 |                 if (isFour) result = "four card";
      |                             ^~~~~~
a.cc:59:48: error: 'result' was not declared in this scope
   59 |                 else if (isThree && Pairs > 0) result = "full house";
      |                                                ^~~~~~
a.cc:60:38: error: 'result' was not declared in this scope
   60 |                 else if (isStraight) result = "straight";
      |                                      ^~~~~~
a.cc:61:35: error: 'result' was not declared in this scope
   61 |                 else if (isThree) result = "three card";
      |                                   ^~~~~~
a.cc:62:38: error: 'result' was not declared in this scope
   62 |                 else if (Pairs == 2) result = "two pairs";
      |                                      ^~~~~~
a.cc:63:37: error: 'result' was not declared in this scope
   63 |                 else if (Pairs > 0) result = "one pair";
      |                                     ^~~~~~
a.cc:65:35: error: 'result' was not declared in this scope
   65 |                 Console.WriteLine(result);
      |                                   ^~~~~~