static class Program{ public static IEnumerable<uint> Digits(this uint X, bool Reverse = true) { do { yield return X % 10; } while ((X /= 10) != 0); } static uint ToUnsignedInt32(this IEnumerable<uint> Digits) { return Digits.Reverse().Aggregate((a, d) => a * 10 + d); } static void Main() { Console.WriteLine( uint.Parse(Console.ReadLine()) .Digits() .Where(d => d % 2 == 1) .ToUnsignedInt32()); Console.ReadKey(); }}