Language: C++

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

namespace AtCoder
{

    static class Program
    {
        static void Main()
        {
            Solve();

            Console.ReadKey();
        }

        static void Solve()
        {
            var N = GetInt();
            List<int> a = new List<int>();
            for(int i=1;Math.Pow(6,i)<= N; i++)
            {
                a.Add((int)Math.Pow(6, i));
            }
            for (int i = 1; Math.Pow(9, i) <= N ; i++)
            {
                a.Add((int)Math.Pow(9, i));
            }
            a = a.OrderBy(o => o).ToList();

            var dp = Enumerable.Repeat(99999999999, N + 1).ToArray();
            dp[0] = 0;
            for(int i = 1; i < N + 1; i++)
            {
                for(int j=0; j<a.Count && 0 <= i-a[j]; j++)
                {
                    dp[i] = Math.Min(dp[i-1] + 1, dp[i - a[j]] + 1);
                }
            }
            var ans = dp[N];

            Console.WriteLine(ans); 
        }


        static public string GetStr() { return Console.ReadLine(); }
        static public int GetInt() { return int.Parse(Console.ReadLine()); }
        static public long GetLong() { return long.Parse(Console.ReadLine()); }
        static public string[] GetStrArray() { return Console.ReadLine().Split(' '); }
        static public int[] GetIntArray() { return Console.ReadLine().Split(' ').Select(int.Parse).ToArray(); }
        static public long[] GetLongArray() { return Console.ReadLine().Split(' ').Select(long.Parse).ToArray(); }
        static public List<double> GetDoubleList() { return Console.ReadLine().Split(' ').Select(double.Parse).ToList(); }
        static public void WriteObjects<T>(IEnumerable<T> values) { foreach (var o in values) { Console.Write(o + " "); } }
        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]);
        }
    }
}

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:5:7: error: expected nested-name-specifier before 'System'
    5 | using System.Threading.Tasks;
      |       ^~~~~~
a.cc:48:16: error: expected unqualified-id before 'public'
   48 |         static public string GetStr() { return Console.ReadLine(); }
      |                ^~~~~~
a.cc:49:16: error: expected unqualified-id before 'public'
   49 |         static public int GetInt() { return int.Parse(Console.ReadLine()); }
      |                ^~~~~~
a.cc:50:16: error: expected unqualified-id before 'public'
   50 |         static public long GetLong() { return long.Parse(Console.ReadLine()); }
      |                ^~~~~~
a.cc:51:16: error: expected unqualified-id before 'public'
   51 |         static public string[] GetStrArray() { return Console.ReadLine().Split(' '); }
      |                ^~~~~~
a.cc:52:16: error: expected unqualified-id before 'public'
   52 |         static public int[] GetIntArray() { return Console.ReadLine().Split(' ').Select(int.Parse).ToArray(); }
      |                ^~~~~~
a.cc:53:16: error: expected unqualified-id before 'public'
   53 |         static public long[] GetLongArray() { return Console.ReadLine().Split(' ').Select(long.Parse).ToArray(); }
      |                ^~~~~~
a.cc:54:16: error: expected unqualified-id before 'public'
   54 |         static public List<double> GetDoubleList() { return Console.ReadLine().Split(' ').Select(double.Parse).ToList(); }
      |                ^~~~~~
a.cc:55:16: error: expected unqualified-id before 'public'
   55 |         static public void WriteObjects<T>(IEnumerable<T> values) { foreach (var o in values) { Console.Write(o + " "); } }
      |                ^~~~~~
a.cc:56:16: error: 'string' does not name a type
   56 |         static string yesno(this bool b) { return b ? "yes" : "no"; }
      |                ^~~~~~
a.cc:57:16: error: 'string' does not name a type
   57 |         static string YesNo(this bool b) { return b ? "Yes" : "No"; }
      |                ^~~~~~
a.cc:58:16: error: 'string' does not name a type
   58 |         static string YESNO(this bool b) { return b ? "YES" : "NO"; }
      |                ^~~~~~
a.cc:60:21: error: expected ';' at end of member declaration
   60 |         static bool eq<T, U>() => typeof(T).Equals(typeof(U));
      |                     ^~
      |                       ;
a.cc:60:23: error: expected unqualified-id before '<' token
   60 |         static bool eq<T, U>() => typeof(T).Equals(typeof(U));
      |                       ^
a.cc:61:16: error: 'T' does not name a type
   61 |         static T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
      |                ^
a.cc:62:16: error: 'T' does not name a type
   62 |         static T cv<T>(string s) => eq<T, int>() ? ct<T, int>(int.Parse(s))
      |                ^
a.cc:67:21: error: variable or field 'Multi' declared void
   67 |         static void Multi<T>(out T a) => a = cv<T>(GetStr());
      |                     ^~~~~
a.cc:67:21: error: expected ';' at end of member declaration
   67 |         static void Multi<T>(out T a) => a = cv<T>(GetStr());
      |                     ^~~~~
      |                          ;
a.cc:67:26: error: expected unqualified-id before '<' token
   67 |         static void Multi<T>(out T a) => a = cv<T>(GetStr());
      |                          ^
a.cc:68:21: error: variable or field 'Multi' declared void
   68 |         static void Multi<T, U>(out T a, out U b)
      |                     ^~~~~
a.cc:68:21: error: expected ';' at end of member declaration
   68 |         static void Multi<T, U>(out T a, out U b)
      |                     ^~~~~
      |                          ;
a.cc:68:26: error: expected unqualified-id before '<' token
   68 |         static void Multi<T, U>(out T a, out U b)
      |                          ^
a.cc:72:21: error: variable or field 'Multi' declared void
   72 |         static void Multi<T, U, V>(out T a, out U b, out V c)
      |                     ^~~~~
a.cc:72:21: error: expected ';' at end of member declaration
   72 |         static void Multi<T, U, V>(out T a, out U b, out V c)
      |                     ^~~~~
      |                          ;
a.cc:72:26: error: expected unqualified-id before '<' token
   72 |         static void Multi<T, U, V>(out T a, out U b, out V c)
      |                          ^
a.cc:76:6: error: expected ';' after class definition
   76 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void AtCoder::Program::Main()':
a.cc:16:13: error: 'Console' was not declared in this scope
   16 |             Console.ReadKey();
      |             ^~~~~~~
a.cc: In static member function 'static void AtCoder::Program::Solve()':
a.cc:21:13: error: 'var' was not declared in this scope
   21 |             var N = GetInt();
      |             ^~~
a.cc:22:13: error: 'List' was not declared in this scope
   22 |             List<int> a = new List<int>();
      |             ^~~~
a.cc:22:18: error: expected primary-expression before 'int'
   22 |             List<int> a = new List<int>();
      |                  ^~~
a.cc:23:25: error: 'Math' was not declared in this scope
   23 |             for(int i=1;Math.Pow(6,i)<= N; i++)
      |                         ^~~~
a.cc:23:41: error: 'N' was not declared in this scope
   23 |             for(int i=1;Math.Pow(6,i)<= N; i++)
      |                                         ^
a.cc:25:17: error: 'a' was not declared in this scope
   25 |                 a.Add((int)Math.Pow(6, i));
      |                 ^
a.cc:27:29: error: 'Math' was not declared in this scope
   27 |             for (int i = 1; Math.Pow(9, i) <= N ; i++)
      |                             ^~~~
a.cc:27:47: error: 'N' was not declared in this scope
   27 |             for (int i = 1; Math.Pow(9, i) <= N ; i++)
      |                                               ^
a.cc:29:17: error: 'a' was not declared in this scope
   29 |                 a.Add((int)Math.Pow(9, i));
      |                 ^
a.cc:31:13: error: 'a' was not declared in this scope
   31 |             a = a.OrderBy(o => o).ToList();
      |             ^
a.cc:31:27: error: 'o' was not declared in this scope
   31 |             a = a.OrderBy(o => o).ToList();
      |                           ^
a.cc:31:30: error: expected primary-expression before '>' token
   31 |             a = a.OrderBy(o => o).ToList();
      |                              ^
a.cc:33:17: error: expected ';' before 'dp'
   33 |             var dp = Enumerable.Repeat(99999999999, N + 1).ToArray();
      |                 ^~
a.cc:34:13: error: 'dp' was not declared in this scope
   34 |             dp[0] = 0;
      |             ^~
a.cc:35:32: error: 'N' was not declared in this scope
   35 |             for(int i = 1; i < N + 1; i++)
      |                                ^
a.cc:39:29: error: 'Math' was not declared in this scope
   39 |                     dp[i] = Math.Min(dp[i-1] + 1, dp[i - a[j]] + 1);
      |                             ^~~~
a.cc:42:17: error: expected ';' before 'ans'
   42 |             var ans = dp[N];
      |                 ^~~
a.cc:44:13: error: 'Console' was not declared in this scope
   44 |             Console.WriteLine(ans);
      |             ^~~~~~~
a.cc:44:31: error: 'ans' was not declared in this scope
   44 |             Console.WriteLine(ans);
      |                               ^~~
a.cc: At global scope:
a.cc:10:5: error: a storage class can only be specified for objects and functions
   10 |     static class Program
      |     ^~~~~~