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using System.Numeric;

static BigInteger Factorial(BigInteger x)
{
    BigInteger result = 1;
    for (BigInteger i = 2; i <= x; i++)
        result *= i;
    return result;
}

static void Main(string[] args)
{
   BigInteger x = BigInteger.Parse(Console.ReadLine());
   Console.WriteLine(Factorial(x).ToString());
}

List<int> oddNumbers = new List<int>();
oddNumbers.Add(1);
oddNumbers.Add(3);
oddNumbers.Add(5);

HashSet<int> numberSet = new HashSet<int>();
numberSet.UnionWith(oddNumbers);
// numberSet contains 1,3,5

int[] evenNumbers = { 2, 4, 6, 2, 6, 4, 2, 4, 6, 2 };
numberSet.UnionWith(evenNumbers); // duplicates are ignored
// numberSet contains 1,2,3,4,5,6

numberSet.ExceptWith(oddNumbers);
// numberSet contains 2,4,6

 

using (Process process = new Process())
{
    process.StartInfo.FileName = "child.exe";
    using (AnonymousPipeServerStream pipeStream = 
        new AnonymousPipeServerStream(PipeDirection.Out,
            HandleInheritability.Inheritable)) 
   {
        process.StartInfo.Arguments =
            pipeStream.GetClientHandleAsString();
        process.StartInfo.UseShellExecute = false;
        process.Start();

        pipeStream.DisposeLocalCopyOfClientHandle();
        using (StreamWriter sw = new StreamWriter(pipeStream)) 
        {
            sw.AutoFlush = true;
            sw.WriteLine(Console.ReadLine());
        }
    }
    process.WaitForExit();
}

 

using (PipeStream pipeStream =
    new AnonymousPipeClientStream(PipeDirection.In, args[0])) 
{    
    using (StreamReader sr = new StreamReader(pipeStream)) 
    {
        string temp;
        while ((temp = sr.ReadLine()) != null) 
        {
            Console.WriteLine(temp);
        }
    }
}

 
using (NamedPipeServerStream pipeStream =
    new NamedPipeServerStream("mypipe")) 
{
    pipeStream.WaitForConnection();
    using (StreamWriter sw = new StreamWriter(pipeStream)) 
    {
        sw.AutoFlush = true;
        sw.WriteLine(Console.ReadLine());
        sw.WriteLine(Console.ReadLine());
    }
}

 
using (NamedPipeClientStream pipeStream =
    new NamedPipeClientStream("mypipe")) 
{
    pipeStream.Connect();
    using (StreamReader sr = new StreamReader(pipeStream)) 
    {
        string temp;
        while ((temp = sr.ReadLine()) != null) {
            Console.WriteLine(temp);
        }
    }
}

 
class MessageWriter 
{
    NamedPipeServerStream m_pipeStream;
    Encoding m_encoding;
    public MessageWriter(NamedPipeServerStream pipeStream,
        Encoding encoding) 
    {
        m_pipeStream = pipeStream;
        m_encoding = encoding;
    }
    public void WriteMessage(string message) 
    {
        Byte[] buffer;
        buffer = m_encoding.GetBytes(message);
        m_pipeStream.Write(buffer, 0, buffer.Length);
    }
}
class MessageReader 
{
    NamedPipeClientStream m_pipeStream;
    Decoder m_decoder;
    Byte[] m_buffer = new Byte[10];
    Char[] m_charBuffer = new Char[10];
    StringBuilder m_stringBuilder = new StringBuilder();
    public MessageReader(NamedPipeClientStream pipeStream,
        Encoding encoding) 
    {
        m_pipeStream = pipeStream;
        m_decoder = encoding.GetDecoder();
    }
    public string ReadMessage() 
    {
        // Clear the StringBuilder
        m_stringBuilder.Length = 0;
        // Read the message
        int bytesRead;
        do {
            bytesRead = m_pipeStream.Read(m_buffer, 0, m_buffer.Length);
            int numChars = m_decoder.GetChars(m_buffer, 0, bytesRead,
                m_charBuffer, 0);
            m_stringBuilder.Append(m_charBuffer, 0, numChars);
        } while (!m_pipeStream.IsMessageComplete);
        // Return the message or null if the pipe has been closed
        if (bytesRead != 0) {
            m_decoder.Reset();
            return m_stringBuilder.ToString();
        }
        else return null;
    }
}

 
using (NamedPipeServerStream pipeStream =
    new NamedPipeServerStream("messagepipe",
    PipeDirection.InOut, 1, PipeTransmissionMode.Message)) 
{
    pipeStream.WaitForConnection();
    MessageWriter mw = new MessageWriter(pipeStream, Encoding.UTF8);
    mw.WriteMessage("Hello World!");
    mw.WriteMessage("Named Pipes Are Cool!");
}

 
using (NamedPipeClientStream pipeStream =
    new NamedPipeClientStream("messagepipe")) 
{
    pipeStream.Connect();
    pipeStream.ReadMode = PipeTransmissionMode.Message;
    MessageReader mr = new MessageReader(pipeStream, Encoding.UTF8);
    string message;
    while ((message = mr.ReadMessage()) != null) 
    {
        Console.WriteLine(message);
    }
}