using System;

using System.Collections.Generic;

​

public interface IPredicate<in T> {

    bool Call(T value);

    IEnumerable<Tout> Filter<Tout>(IEnumerable<Tout> values) where Tout: T;

    // IEnumerable<T> Filter2(IEnumerable<T> values);

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}