Language: C++

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static System.Math;
using System.Text;
using System.Threading;
using System.Globalization;
using System.Runtime.CompilerServices;
using Library;

namespace Program
{
    public static class ProblemA
    {
        static bool SAIKI = false;
        static public int numberOfRandomCases = 0;
        static public void MakeTestCase(List<string> _input, List<string> _output, ref Func<string[], bool> _outputChecker)
        {
        }
        static public void Solve()
        {
            var N = NN;
            var S = NS;
            var first = S.Substring(0, (int)N).ToArray();
            var second = S.Substring((int)N).Reverse().ToArray();
            var firstCounter = new LIB_Dict<string, long>();
            var secondCounter = new LIB_Dict<string, long>();
            var ten = LIB_Math.Pow(2, N);
            for (var i = 0; i < ten; i++)
            {
                var ary = new List<long>();
                var ary2 = new List<long>();
                for (var j = 0; j < N; j++)
                {
                    if (LIB_BitUtil.IsSet(i, j)) ary.Add(first[j]);
                    else ary2.Add(first[j]);
                }
                firstCounter[ary.Join() + "," + ary2.Join()]++;
            }
            for (var i = 0; i < ten; i++)
            {
                var ary = new List<long>();
                var ary2 = new List<long>();
                for (var j = 0; j < N; j++)
                {
                    if (LIB_BitUtil.IsSet(i, j)) ary.Add(second[j]);
                    else ary2.Add(second[j]);
                }
                secondCounter[ary.Join() + "," + ary2.Join()]++;
            }
            var ans = 0L;
            foreach (var item in firstCounter)
            {
                ans += item.Value * secondCounter[item.Key];
            }
            Console.WriteLine(ans);
        }
        class Printer : StreamWriter
        {
            public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
            public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { base.AutoFlush = false; }
            public Printer(Stream stream, Encoding encoding) : base(stream, encoding) { base.AutoFlush = false; }
        }
        static LIB_FastIO fastio = new LIB_FastIODebug();
        static public void Main(string[] args) { if (args.Length == 0) { fastio = new LIB_FastIO(); Console.SetOut(new Printer(Console.OpenStandardOutput())); } if (SAIKI) { var t = new Thread(Solve, 134217728); t.Start(); t.Join(); } else Solve(); Console.Out.Flush(); }
        static long NN => fastio.Long();
        static double ND => fastio.Double();
        static string NS => fastio.Scan();
        static long[] NNList(long N) => Repeat(0, N).Select(_ => NN).ToArray();
        static double[] NDList(long N) => Repeat(0, N).Select(_ => ND).ToArray();
        static string[] NSList(long N) => Repeat(0, N).Select(_ => NS).ToArray();
        static long Count<T>(this IEnumerable<T> x, Func<T, bool> pred) => Enumerable.Count(x, pred);
        static IEnumerable<T> Repeat<T>(T v, long n) => Enumerable.Repeat<T>(v, (int)n);
        static IEnumerable<int> Range(long s, long c) => Enumerable.Range((int)s, (int)c);
        static IOrderedEnumerable<T> OrderByRand<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x, _ => xorshift);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x) => Enumerable.OrderBy(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderBy<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderBy(x.OrderByRand(), selector);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x) => Enumerable.OrderByDescending(x.OrderByRand(), e => e);
        static IOrderedEnumerable<T1> OrderByDescending<T1, T2>(this IEnumerable<T1> x, Func<T1, T2> selector) => Enumerable.OrderByDescending(x.OrderByRand(), selector);
        static IOrderedEnumerable<string> OrderBy(this IEnumerable<string> x) => x.OrderByRand().OrderBy(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderBy<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderBy(selector, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<string> OrderByDescending(this IEnumerable<string> x) => x.OrderByRand().OrderByDescending(e => e, StringComparer.OrdinalIgnoreCase);
        static IOrderedEnumerable<T> OrderByDescending<T>(this IEnumerable<T> x, Func<T, string> selector) => x.OrderByRand().OrderByDescending(selector, StringComparer.OrdinalIgnoreCase);
        static string Join<T>(this IEnumerable<T> x, string separator = "") => string.Join(separator, x);
        static uint xorshift { get { _xsi.MoveNext(); return _xsi.Current; } }
        static IEnumerator<uint> _xsi = _xsc();
        static IEnumerator<uint> _xsc() { uint x = 123456789, y = 362436069, z = 521288629, w = (uint)(DateTime.Now.Ticks & 0xffffffff); while (true) { var t = x ^ (x << 11); x = y; y = z; z = w; w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)); yield return w; } }
    }
}
namespace Library {
    class LIB_Math
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public IEnumerable<long> Primes(long x)
        {
            if (x < 2) yield break;
            yield return 2;
            var halfx = x / 2;
            var table = new bool[halfx + 1];
            var max = (long)(Math.Sqrt(x) / 2);
            for (long i = 1; i <= max; ++i)
            {
                if (table[i]) continue;
                var add = 2 * i + 1;
                yield return add;
                for (long j = 2 * i * (i + 1); j <= halfx; j += add)
                    table[j] = true;
            }
            for (long i = max + 1; i <= halfx; ++i)
                if (!table[i] && 2 * i + 1 <= x)
                    yield return 2 * i + 1;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public IEnumerable<long> Factors(long x)
        {
            if (x < 2) yield break;
            while (x % 2 == 0)
            {
                x /= 2; yield return 2;
            }
            var max = (long)Math.Sqrt(x);
            for (long i = 3; i <= max; i += 2)
            {
                while (x % i == 0)
                {
                    x /= i; yield return i;
                }
            }
            if (x != 1) yield return x;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public IEnumerable<long> Divisor(long x)
        {
            if (x < 1) yield break;
            var max = (long)Math.Sqrt(x);
            for (long i = 1; i <= max; ++i)
            {
                if (x % i != 0) continue;
                yield return i;
                if (i != x / i) yield return x / i;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long GCD(long a, long b)
        {
            while (b > 0)
            {
                var tmp = b;
                b = a % b;
                a = tmp;
            }
            return a;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long LCM(long a, long b) => a / GCD(a, b) * b;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long Pow(long x, long y)
        {
            long a = 1;
            while (y != 0)
            {
                if ((y & 1) == 1) a *= x;
                if (x < long.MaxValue / x) x *= x;
                y >>= 1;
            }
            return a;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public decimal Sqrt(decimal x)
        {
            decimal prev, cur = (decimal)Math.Sqrt((double)x);
            do
            {
                prev = cur;
                if (prev == 0) return 0;
                cur = (prev + x / prev) / 2;
            } while (cur != prev);
            return cur;
        }
        static List<long> _fact = new List<long>() { 1 };
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static void Build(long n)
        {
            if (n >= _fact.Count)
                for (int i = _fact.Count; i <= n; ++i) _fact.Add(_fact[i - 1] * i);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long Comb(long n, long k)
        {
            Build(n);
            if (n == 0 && k == 0) return 1;
            if (n < k || n < 0) return 0;
            return _fact[(int)n] / _fact[(int)(n - k)] / _fact[(int)k];
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long Perm(long n, long k)
        {
            Build(n);
            if (n == 0 && k == 0) return 1;
            if (n < k || n < 0) return 0;
            return _fact[(int)n] / _fact[(int)(n - k)];
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public IEnumerable<List<int>> MakePermutation(long n, bool zeroIndexed = true)
        {
            if (n <= 0) throw new Exception();
            var c = new int[n];
            var a = new int[n];
            if (!zeroIndexed) a[0] = 1;
            for (var i = 1; i < n; i++) a[i] = a[i - 1] + 1;
            yield return new List<int>(a);
            for (var i = 0; i < n;)
            {
                if (c[i] < i)
                {
                    if (i % 2 == 0)
                    {
                        var t = a[0]; a[0] = a[i]; a[i] = t;
                    }
                    else
                    {
                        var t = a[c[i]]; a[c[i]] = a[i]; a[i] = t;
                    }
                    yield return new List<int>(a);
                    ++c[i];
                    i = 0;
                }
                else
                {
                    c[i] = 0;
                    ++i;
                }
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public bool NextPermutation(long[] ary)
        {
            var n = ary.Length;
            var i = n - 1;
            while (i - 1 >= 0 && ary[i - 1] > ary[i]) --i;
            if (i == 0) return false;
            var j = i;
            while (j + 1 < n && ary[i - 1] < ary[j + 1]) ++j;
            var tmp = ary[i - 1]; ary[i - 1] = ary[j]; ary[j] = tmp;
            var s = i;
            var t = n - 1;
            while (t - s > 0)
            {
                tmp = ary[t]; ary[t] = ary[s]; ary[s] = tmp;
                ++s; --t;
            }
            return true;
        }
    }
    class LIB_FastIO
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_FastIO() { str = Console.OpenStandardInput(); }
        readonly Stream str;
        readonly byte[] buf = new byte[1024];
        int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return isEof; }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        byte read()
        {
            if (isEof) throw new EndOfStreamException();
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        char Char()
        {
            byte b = 0;
            do b = read();
            while (b < 33 || 126 < b);
            return (char)b;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public long Long()
        {
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != '-' && (b < '0' || '9' < b));
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        virtual public double Double() { return double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
    class LIB_FastIODebug : LIB_FastIO
    {
        Queue<string> param = new Queue<string>();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        string NextString() { if (param.Count == 0) foreach (var item in Console.ReadLine().Split(' ')) param.Enqueue(item); return param.Dequeue(); }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_FastIODebug() { }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override string Scan() => NextString();
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override long Long() => long.Parse(NextString());
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override double Double() => double.Parse(NextString());
    }
    class LIB_BitUtil
    {
        public static readonly ulong[] BitMask;
        static LIB_BitUtil()
        {
            BitMask = new ulong[64];
            BitMask[0] = 1;
            for (var i = 1; i < 64; i++) BitMask[i] = BitMask[i - 1] << 1;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public IEnumerable<long> ScanOne(long value)
        {
            for (; value > 0; value &= value - 1) yield return value & -value;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long PopCount(ulong value)
        {
            value = (value & 0x5555555555555555) + ((value >> 1) & 0x5555555555555555);
            value = (value & 0x3333333333333333) + ((value >> 2) & 0x3333333333333333);
            value = (value & 0x0f0f0f0f0f0f0f0f) + ((value >> 4) & 0x0f0f0f0f0f0f0f0f);
            value = (value & 0x00ff00ff00ff00ff) + ((value >> 8) & 0x00ff00ff00ff00ff);
            value = (value & 0x0000ffff0000ffff) + ((value >> 16) & 0x0000ffff0000ffff);
            value = (value & 0x00000000ffffffff) + ((value >> 32) & 0x00000000ffffffff);
            return (long)value;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public long PopCount(long value) => PopCount((ulong)value);
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public bool IsSet(ulong value, int idx) => (value & BitMask[idx]) != 0;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        static public bool IsSet(long value, int idx) => IsSet((ulong)value, idx);
    }
    class LIB_Dict<K, V> : Dictionary<K, V>
    {
        Func<K, V> d;
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Dict(Func<K, V> _d) { d = _d; }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public LIB_Dict() : this(_ => default(V)) { }
        new public V this[K i]
        {
            get
            {
                V v;
                return TryGetValue(i, out v) ? v : base[i] = d(i);
            }
            set
            {
                base[i] = value;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override int GetHashCode()
        {
            unchecked
            {
                var ret = 23;
                for (var e = GetEnumerator(); e.MoveNext();) ret = (ret * 37) ^ (e.Current.Key.GetHashCode() << 5 + e.Current.Key.GetHashCode()) ^ e.Current.Value.GetHashCode();
                return ret;
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public override bool Equals(object obj)
        {
            var o = (LIB_Dict<K, V>)obj;
            foreach (var kv in o)
            {
                if (!ContainsKey(kv.Key) || !this[kv.Key].Equals(kv.Value))
                    return false;
            }
            return o.Count == Count;
        }
    }
}


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 'static'
    5 | using static System.Math;
      |       ^~~~~~
a.cc:6:7: error: expected nested-name-specifier before 'System'
    6 | using System.Text;
      |       ^~~~~~
a.cc:7:7: error: expected nested-name-specifier before 'System'
    7 | using System.Threading;
      |       ^~~~~~
a.cc:8:7: error: expected nested-name-specifier before 'System'
    8 | using System.Globalization;
      |       ^~~~~~
a.cc:9:7: error: expected nested-name-specifier before 'System'
    9 | using System.Runtime.CompilerServices;
      |       ^~~~~~
a.cc:10:7: error: expected nested-name-specifier before 'Library'
   10 | using Library;
      |       ^~~~~~~
a.cc:14:5: error: expected unqualified-id before 'public'
   14 |     public static class ProblemA
      |     ^~~~~~
a.cc:94:9: error: expected unqualified-id before '[' token
   94 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:114:9: error: expected unqualified-id before '[' token
  114 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:132:9: error: expected unqualified-id before '[' token
  132 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:144:9: error: expected unqualified-id before '[' token
  144 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:155:9: error: expected unqualified-id before '[' token
  155 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:157:9: error: expected unqualified-id before '[' token
  157 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:169:9: error: expected unqualified-id before '[' token
  169 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:181:16: error: 'List' does not name a type
  181 |         static List<long> _fact = new List<long>() { 1 };
      |                ^~~~
a.cc:182:9: error: expected unqualified-id before '[' token
  182 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:188:9: error: expected unqualified-id before '[' token
  188 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:196:9: error: expected unqualified-id before '[' token
  196 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:204:9: error: expected unqualified-id before '[' token
  204 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:236:9: error: expected unqualified-id before '[' token
  236 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:255:6: error: expected ';' after class definition
  255 |     }
      |      ^
      |      ;
a.cc:258:9: error: expected unqualified-id before '[' token
  258 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:260:9: error: 'readonly' does not name a type
  260 |         readonly Stream str;
      |         ^~~~~~~~
a.cc:261:9: error: 'readonly' does not name a type
  261 |         readonly byte[] buf = new byte[1024];
      |         ^~~~~~~~
a.cc:263:15: error: expected ':' before 'bool'
  263 |         public bool isEof = false;
      |               ^~~~~
      |               :
a.cc:264:15: error: expected ':' before 'bool'
  264 |         public bool IsEndOfStream
      |               ^~~~~
      |               :
a.cc:268:9: error: expected ';' at end of member declaration
  268 |         }
      |         ^
      |          ;
a.cc:269:9: error: expected unqualified-id before '[' token
  269 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:284:9: error: expected unqualified-id before '[' token
  284 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:292:9: error: expected unqualified-id before '[' token
  292 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:300:9: error: expected unqualified-id before '[' token
  300 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:314:9: error: expected unqualified-id before '[' token
  314 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:316:6: error: expected ';' after class definition
  316 |     }
      |      ^
      |      ;
a.cc:266:25: error: 'MethodImplOptions' was not declared in this scope
  266 |             [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |                         ^~~~~~~~~~~~~~~~~
a.cc: In lambda function:
a.cc:267:13: error: expected '{' before 'get'
  267 |             get { return isEof; }
      |             ^~~
a.cc: At global scope:
a.cc:267:13: error: expected '}' before 'get'
a.cc:265:9: note: to match this '{'
  265 |         {
      |         ^
a.cc:267:13: warning: narrowing conversion of 'Library::LIB_FastIO::<lambda()>::_FUN' from 'void (*)()' to 'bool' [-Wnarrowing]
  267 |             get { return isEof; }
      |             ^~~
a.cc:267:13: error: expected ';' before 'get'
a.cc:319:9: error: 'Queue' does not name a type
  319 |         Queue<string> param = new Queue<string>();
      |         ^~~~~
a.cc:320:9: error: expected unqualified-id before '[' token
  320 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:322:9: error: expected unqualified-id before '[' token
  322 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:324:9: error: expected unqualified-id before '[' token
  324 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:326:9: error: expected unqualified-id before '[' token
  326 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:328:9: error: expected unqualified-id before '[' token
  328 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:330:6: error: expected ';' after class definition
  330 |     }
      |      ^
      |      ;
a.cc:333:15: error: expected ':' before 'static'
  333 |         public static readonly ulong[] BitMask;
      |               ^~~~~~~
      |               :
a.cc:333:23: error: 'readonly' does not name a type
  333 |         public static readonly ulong[] BitMask;
      |                       ^~~~~~~~
a.cc:334:9: error: constructor cannot be static member function
  334 |         static LIB_BitUtil()
      |         ^~~~~~
a.cc:340:9: error: expected unqualified-id before '[' token
  340 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:345:9: error: expected unqualified-id before '[' token
  345 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:356:9: error: expected unqualified-id before '[' token
  356 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:358:9: error: expected unqualified-id before '[' token
  358 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:360:9: error: expected unqualified-id before '[' token
  360 |         [MethodImpl(MethodImplOptions.AggressiveInlining)]
      |         ^
a.cc:362:6: error: expected ';' after class definition
  362 |     }
      |      ^
      |      ;
a.cc: In constructor 'Library::LIB_BitUtil::LIB_BitUtil()':
a.cc:336:13: error: 'BitMask' was not declared in this scope
  336 |             BitMask = new ulong[64];
      |             ^~~~~~~
a.cc:336:27: error: 'ulong' does not name a type; did you mean 'long'?
  336 |             BitMask = new ulong[64];
      |                           ^~~~~
      |                           long
a.cc:338:18: error: 'var' was not declared in this scope
  338 |             for (var i = 1; i < 64; i++) BitMask[i] = BitMask[i - 1] << 1;
      |                  ^~~
a.cc:338:29: error: 'i' was not declared in this scope
  338 |             for (var i = 1; i < 64; i++) BitMask[i] = BitMask[i - 1] << 1;
      |                             ^
a.cc: At global scope:
a.cc:363:11: error: 'LIB_Dict' is not a class template
  363 |     class LIB_Dict<K, V> : Dictionary<K, V>
      |           ^~~~~~~~
a.cc:363:20: error: 'K' was not declared in this scope
  363 |     class LIB_Dict<K, V> : Dictionary<K, V>
      |                    ^
a.cc:363:23: error: 'V' was not declared in this scope
  363 |     class LIB_Dict<K, V> : Dictionary<K, V>
      |                       ^
a.cc:363:38: error: expected template-name before '<' token
  363 |     class LIB_Dict<K, V> : Dictionary<K, V>
      |                                      ^
a.cc:363:38: error: expected '{' before '<' token
a.cc:363:38: error: expected unqualified-id before '<' token