C# declaration of namespaces

Question

Hi,

This is my first time in C# programming.Below is my simple program on while loop.
May I know how to declare namespace for using int?
And where can I look for this namespace information.

Thanks

using System;

public class WhileLoop()

{

public static void Main(string[] args)

{

int i = 0;

while ( i < 5 )

{

Console.WriteLine ( i );

++i;

}

}

}

}