class Program
{
    IEnumerable<int> Infinity()
    {
        int i = 1;
        while (true)
        {
            yield return i++;
        }
    }
}

class Program
{
    IEnumerable<int> Infinity() { return new InfinityEnumerable(); }

    class InfinityEnumerable : IEnumerable<int>
    {
        IEnumerator<int> GetEnumerator() { return new InfinityEnumerator(); }
    }

    class InifityEnumerator : IEnumerator<int>
    {
        public InfinityEnumerator() { this.Current = 1; }
        public int Current { get; private set; }
        bool MoveNext() { this.Current++; return true; }
    }
}