Language: C++

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder
{

    static class Program
    {
        static void Main()
        {
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });

            var N = GetInt();
            var dic = new Dictionary<int, int>();
            for(int i = 0; i < N; i++)
            {
                var cin = GetInt();
                if (dic.ContainsKey(cin) == false)
                {
                    dic.Add(cin, 0);
                }
                dic[cin]++;
            }
            var ans = dic.Values.Count(c => c % 2 == 1);

            Console.WriteLine(ans);

            Console.Out.Flush();
            Console.ReadKey();
        }


        static public string GetStr() { return Console.ReadLine().Trim(); }
        static public char GetChar() { return Console.ReadLine().Trim()[0]; }
        static public int GetInt() { return int.Parse(Console.ReadLine().Trim()); }
        static public long GetLong() { return long.Parse(Console.ReadLine().Trim()); }
        static public double GetDouble() { return double.Parse(Console.ReadLine().Trim()); }
        static public string[] GetStrArray() { return Console.ReadLine().Trim().Split(' '); }
        static public int[] GetIntArray() { return Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray(); }
        static public long[] GetLongArray() { return Console.ReadLine().Trim().Split(' ').Select(long.Parse).ToArray(); }
        static public char[] GetCharArray() { return Console.ReadLine().Trim().Split(' ').Select(char.Parse).ToArray(); }
        static public Double[] GetDoubleArray() { return Console.ReadLine().Trim().Split(' ').Select(double.Parse).ToArray(); }
        static public void WriteObjects<T>(IList<T> values) { var num = values.Count; for (int i = 0; i < num; i++) { Console.Write(values[i]); if (i < num - 1) { Console.Write(" "); } } Console.WriteLine(); }
        static string yesno(this bool b) { return b ? "yes" : "no"; }
        static string YesNo(this bool b) { return b ? "Yes" : "No"; }
        static string YESNO(this bool b) { return b ? "YES" : "NO"; }

        static bool eq<T, U>() => typeof(T).Equals(typeof(U));
        static T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
        static T cv<T>(string s) => eq<T, int>() ? ct<T, int>(int.Parse(s))
                           : eq<T, long>() ? ct<T, long>(long.Parse(s))
                           : eq<T, double>() ? ct<T, double>(double.Parse(s))
                           : eq<T, char>() ? ct<T, char>(s[0])
                                             : ct<T, string>(s);
        static void Multi<T>(out T a) => a = cv<T>(GetStr());
        static void Multi<T, U>(out T a, out U b)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]);
        }
        static void Multi<T, U, V>(out T a, out U b, out V c)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]);
        }
        static void Multi<T, U, V,W>(out T a, out U b, out V c, out W d)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]);
        }
        static void Multi<T, U, V, W,X>(out T a, out U b, out V c, out W d,out X e)
        {
            var ar = GetStrArray(); a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]);e = cv<X>(ar[4]);
        }
    }
}

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.IO;
      |       ^~~~~~
a.cc:4:7: error: expected nested-name-specifier before 'System'
    4 | using System.Linq;
      |       ^~~~~~
a.cc:5:7: error: expected nested-name-specifier before 'System'
    5 | using System.Text;
      |       ^~~~~~
a.cc:6:7: error: expected nested-name-specifier before 'System'
    6 | using System.Threading.Tasks;
      |       ^~~~~~
a.cc:37:16: error: expected unqualified-id before 'public'
   37 |         static public string GetStr() { return Console.ReadLine().Trim(); }
      |                ^~~~~~
a.cc:38:16: error: expected unqualified-id before 'public'
   38 |         static public char GetChar() { return Console.ReadLine().Trim()[0]; }
      |                ^~~~~~
a.cc:39:16: error: expected unqualified-id before 'public'
   39 |         static public int GetInt() { return int.Parse(Console.ReadLine().Trim()); }
      |                ^~~~~~
a.cc:40:16: error: expected unqualified-id before 'public'
   40 |         static public long GetLong() { return long.Parse(Console.ReadLine().Trim()); }
      |                ^~~~~~
a.cc:41:16: error: expected unqualified-id before 'public'
   41 |         static public double GetDouble() { return double.Parse(Console.ReadLine().Trim()); }
      |                ^~~~~~
a.cc:42:16: error: expected unqualified-id before 'public'
   42 |         static public string[] GetStrArray() { return Console.ReadLine().Trim().Split(' '); }
      |                ^~~~~~
a.cc:43:16: error: expected unqualified-id before 'public'
   43 |         static public int[] GetIntArray() { return Console.ReadLine().Trim().Split(' ').Select(int.Parse).ToArray(); }
      |                ^~~~~~
a.cc:44:16: error: expected unqualified-id before 'public'
   44 |         static public long[] GetLongArray() { return Console.ReadLine().Trim().Split(' ').Select(long.Parse).ToArray(); }
      |                ^~~~~~
a.cc:45:16: error: expected unqualified-id before 'public'
   45 |         static public char[] GetCharArray() { return Console.ReadLine().Trim().Split(' ').Select(char.Parse).ToArray(); }
      |                ^~~~~~
a.cc:46:16: error: expected unqualified-id before 'public'
   46 |         static public Double[] GetDoubleArray() { return Console.ReadLine().Trim().Split(' ').Select(double.Parse).ToArray(); }
      |                ^~~~~~
a.cc:47:16: error: expected unqualified-id before 'public'
   47 |         static public void WriteObjects<T>(IList<T> values) { var num = values.Count; for (int i = 0; i < num; i++) { Console.Write(values[i]); if (i < num - 1) { Console.Write(" "); } } Console.WriteLine(); }
      |                ^~~~~~
a.cc:48:16: error: 'string' does not name a type
   48 |         static string yesno(this bool b) { return b ? "yes" : "no"; }
      |                ^~~~~~
a.cc:49:16: error: 'string' does not name a type
   49 |         static string YesNo(this bool b) { return b ? "Yes" : "No"; }
      |                ^~~~~~
a.cc:50:16: error: 'string' does not name a type
   50 |         static string YESNO(this bool b) { return b ? "YES" : "NO"; }
      |                ^~~~~~
a.cc:52:21: error: expected ';' at end of member declaration
   52 |         static bool eq<T, U>() => typeof(T).Equals(typeof(U));
      |                     ^~
      |                       ;
a.cc:52:23: error: expected unqualified-id before '<' token
   52 |         static bool eq<T, U>() => typeof(T).Equals(typeof(U));
      |                       ^
a.cc:53:16: error: 'T' does not name a type
   53 |         static T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
      |                ^
a.cc:54:16: error: 'T' does not name a type
   54 |         static T cv<T>(string s) => eq<T, int>() ? ct<T, int>(int.Parse(s))
      |                ^
a.cc:59:21: error: variable or field 'Multi' declared void
   59 |         static void Multi<T>(out T a) => a = cv<T>(GetStr());
      |                     ^~~~~
a.cc:59:21: error: expected ';' at end of member declaration
   59 |         static void Multi<T>(out T a) => a = cv<T>(GetStr());
      |                     ^~~~~
      |                          ;
a.cc:59:26: error: expected unqualified-id before '<' token
   59 |         static void Multi<T>(out T a) => a = cv<T>(GetStr());
      |                          ^
a.cc:60:21: error: variable or field 'Multi' declared void
   60 |         static void Multi<T, U>(out T a, out U b)
      |                     ^~~~~
a.cc:60:21: error: expected ';' at end of member declaration
   60 |         static void Multi<T, U>(out T a, out U b)
      |                     ^~~~~
      |                          ;
a.cc:60:26: error: expected unqualified-id before '<' token
   60 |         static void Multi<T, U>(out T a, out U b)
      |                          ^
a.cc:64:21: error: variable or field 'Multi' declared void
   64 |         static void Multi<T, U, V>(out T a, out U b, out V c)
      |                     ^~~~~
a.cc:64:21: error: expected ';' at end of member declaration
   64 |         static void Multi<T, U, V>(out T a, out U b, out V c)
      |                     ^~~~~
      |                          ;
a.cc:64:26: error: expected unqualified-id before '<' token
   64 |         static void Multi<T, U, V>(out T a, out U b, out V c)
      |                          ^
a.cc:68:21: error: variable or field 'Multi' declared void
   68 |         static void Multi<T, U, V,W>(out T a, out U b, out V c, out W d)
      |                     ^~~~~
a.cc:68:21: error: expected ';' at end of member declaration
   68 |         static void Multi<T, U, V,W>(out T a, out U b, out V c, out W d)
      |                     ^~~~~
      |                          ;
a.cc:68:26: error: expected unqualified-id before '<' token
   68 |         static void Multi<T, U, V,W>(out T a, out U b, out V c, out W d)
      |                          ^
a.cc:72:21: error: variable or field 'Multi' declared void
   72 |         static void Multi<T, U, V, W,X>(out T a, out U b, out V c, out W d,out X e)
      |                     ^~~~~
a.cc:72:21: error: expected ';' at end of member declaration
   72 |         static void Multi<T, U, V, W,X>(out T a, out U b, out V c, out W d,out X e)
      |                     ^~~~~
      |                          ;
a.cc:72:26: error: expected unqualified-id before '<' token
   72 |         static void Multi<T, U, V, W,X>(out T a, out U b, out V c, out W d,out X e)
      |                          ^
a.cc:76:6: error: expected ';' after class definition
   76 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void AtCoder::Program::Main()':
a.cc:15:13: error: 'Console' was not declared in this scope
   15 |             Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
      |             ^~~~~~~
a.cc:15:32: error: expected type-specifier before 'StreamWriter'
   15 |             Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
      |                                ^~~~~~~~~~~~
a.cc:17:13: error: 'var' was not declared in this scope
   17 |             var N = GetInt();
      |             ^~~
a.cc:18:17: error: expected ';' before 'dic'
   18 |             var dic = new Dictionary<int, int>();
      |                 ^~~
a.cc:19:32: error: 'N' was not declared in this scope
   19 |             for(int i = 0; i < N; i++)
      |                                ^
a.cc:21:21: error: expected ';' before 'cin'
   21 |                 var cin = GetInt();
      |                     ^~~
a.cc:22:21: error: 'dic' was not declared in this scope
   22 |                 if (dic.ContainsKey(cin) == false)
      |                     ^~~
a.cc:22:37: error: 'cin' was not declared in this scope
   22 |                 if (dic.ContainsKey(cin) == false)
      |                                     ^~~
a.cc:26:17: error: 'dic' was not declared in this scope
   26 |                 dic[cin]++;
      |                 ^~~
a.cc:26:21: error: 'cin' was not declared in this scope
   26 |                 dic[cin]++;
      |                     ^~~
a.cc:28:17: error: expected ';' before 'ans'
   28 |             var ans = dic.Values.Count(c => c % 2 == 1);
      |                 ^~~
a.cc:30:31: error: 'ans' was not declared in this scope
   30 |             Console.WriteLine(ans);
      |                               ^~~
a.cc: At global scope:
a.cc:11:5: error: a storage class can only be specified for objects and functions
   11 |     static class Program
      |     ^~~~~~