#pragma warning disable CS0436
using System;
namespace System {
    public readonly ref struct Index {
        public Index(int value, bool fromEnd = false) {
        }
    }
}
namespace ConsoleApp1 {
    interface I<T> {
        ref readonly T this[Index index] { get; }
    }
    class Program {
        static ref readonly T f<T>(I<T> i) {
            return ref i[new Index(1, true)];
        }
        static ref readonly T h<T>(I<T> i) {
            return ref i[^1];
        }
        static void Main(string[] args) {
            Console.WriteLine("Hello World!");
        }
    }
}