class Program
    {
        //GetLength(1)-столбцы

        static void Main(string[] args)
        {
          Console.WriteLine("Enter string:");
            StringBuilder strB = new StringBuilder(Console.ReadLine());
            byte[] CountCh = new byte[65536];

            for (int i = 0; i < strB.Length; i++)
                CountCh[strB[i]]++;

            char chMax = (char)Array.IndexOf(CountCh, CountCh.Max());
            strB = strB.Replace(chMax.ToString(), "");
            Console.WriteLine(strB);
        }
    }