Language: C++

namespace ABCDEF
{
    //begin using
    using System;
    using System.Text;
    using System.Collections.Generic;
    using System.Linq;
    using System.IO;
    using System.Globalization;
    using System.Numerics;
    using Comp.IO;

    //end using 

    class Solver
    {
        public void Solve()
        {
            double t = cin.NextInt();
            double x = cin.NextInt();
            Console.WriteLine(t/x);


        }
        static Scanner<Stream> cin = new Scanner<Stream>(Console.OpenStandardInput());
        static Printer cout = new Printer(Console.OpenStandardOutput()) { AutoFlush = false };
        public static void Main(string[] args)
        {
            //var file = new Scanner<FileStream>(new FileStream("temp.txt", FileMode.Append));
            Console.SetOut(cout);
            new Solver().Solve();
            Console.Out.Flush();
        }
    }

    //begin auxiliary class

    //end auxiliary class
}
namespace Comp.IO
{
    using System;
    using System.Text;
    using System.IO;
    using System.Globalization;
    using System.Numerics;

    public class Scanner<T>
    where T : Stream
    {
        public Scanner(T stream) { str = stream; }
        private readonly T str;
        private byte[] buf = new byte[1024];
        private int len, itr;
        public bool isEof = false;
        // public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) throw new EndOfStreamException();
            if (itr >= len)
            {
                itr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[itr++];
        }
        public char NextChar()
        {
            byte b = 0;
            do b = read();
            while (b < 33 || 126 < b);
            return (char)b;
        }
        public string NextString()
        {
            var sb = new StringBuilder();
            char c = NextChar();
            while (c >= 33 && c <= 126) { sb.Append(c); c = (char)read(); }
            return sb.ToString();
        }
        public long NextLong()
        {
            long ret = 0; byte b = 0; var negative = false;
            do b = read();
            while (b != '-' && (b < '0' || '9' < b));
            if (b == '-') { negative = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return negative ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int NextInt() { return (int)NextLong(); }
        public ulong NextUlong() { return ulong.Parse(NextString()); }
        public double NextDouble() { return double.Parse(NextString(), CultureInfo.InvariantCulture); }
        public decimal NextDecimal() { return decimal.Parse(NextString()); }
    }
    class Printer : StreamWriter
    {
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(Stream stream, Encoding encoding) : base(stream, encoding) { }
    }
}


Compiler output:
a.cc:4:11: error: expected nested-name-specifier before 'System'
    4 |     using System;
      |           ^~~~~~
a.cc:5:11: error: expected nested-name-specifier before 'System'
    5 |     using System.Text;
      |           ^~~~~~
a.cc:6:11: error: expected nested-name-specifier before 'System'
    6 |     using System.Collections.Generic;
      |           ^~~~~~
a.cc:7:11: error: expected nested-name-specifier before 'System'
    7 |     using System.Linq;
      |           ^~~~~~
a.cc:8:11: error: expected nested-name-specifier before 'System'
    8 |     using System.IO;
      |           ^~~~~~
a.cc:9:11: error: expected nested-name-specifier before 'System'
    9 |     using System.Globalization;
      |           ^~~~~~
a.cc:10:11: error: expected nested-name-specifier before 'System'
   10 |     using System.Numerics;
      |           ^~~~~~
a.cc:11:11: error: expected nested-name-specifier before 'Comp'
   11 |     using Comp.IO;
      |           ^~~~
a.cc:17:15: error: expected ':' before 'void'
   17 |         public void Solve()
      |               ^~~~~
      |               :
a.cc:25:16: error: 'Scanner' does not name a type
   25 |         static Scanner<Stream> cin = new Scanner<Stream>(Console.OpenStandardInput());
      |                ^~~~~~~
a.cc:26:16: error: 'Printer' does not name a type
   26 |         static Printer cout = new Printer(Console.OpenStandardOutput()) { AutoFlush = false };
      |                ^~~~~~~
a.cc:27:15: error: expected ':' before 'static'
   27 |         public static void Main(string[] args)
      |               ^~~~~~~
      |               :
a.cc:27:33: error: 'string' has not been declared
   27 |         public static void Main(string[] args)
      |                                 ^~~~~~
a.cc:27:42: error: expected ',' or '...' before 'args'
   27 |         public static void Main(string[] args)
      |                                          ^~~~
a.cc:34:6: error: expected ';' after class definition
   34 |     }
      |      ^
      |      ;
a.cc: In member function 'void ABCDEF::Solver::Solve()':
a.cc:19:24: error: 'cin' was not declared in this scope
   19 |             double t = cin.NextInt();
      |                        ^~~
a.cc:21:13: error: 'Console' was not declared in this scope
   21 |             Console.WriteLine(t/x);
      |             ^~~~~~~
a.cc: In static member function 'static void ABCDEF::Solver::Main(int*)':
a.cc:30:13: error: 'Console' was not declared in this scope
   30 |             Console.SetOut(cout);
      |             ^~~~~~~
a.cc:30:28: error: 'cout' was not declared in this scope
   30 |             Console.SetOut(cout);
      |                            ^~~~
a.cc:31:25: error: expected ';' before '.' token
   31 |             new Solver().Solve();
      |                         ^
a.cc: At global scope:
a.cc:40:15: error: expected '{' before '.' token
   40 | namespace Comp.IO
      |               ^
a.cc:40:15: error: expected unqualified-id before '.' token