using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter the string");

        string sentence = Console.ReadLine();

        CalculateFrequencyIgnoringSpecial(sentence);

    }

    static void CalculateFrequencyIgnoringSpecial(string sentence)

    {

        int[] counter = new int[26];

        sentence = sentence.ToLower();

        foreach(char c in sentence)

        {

            if(char.IsLetter(c))

            {

                counter[(c)-'a']++;

            }

        }

        int max =0;

        char value ='0';

        foreach(char c in sentence)

        {

            //Console.WriteLine(counter[(int)c-'a']);

            if(char.IsLetter(c))

            {

                if(max <counter[(int)c-'a'])

                {

                    max = counter[(int)c-'a'];

                    value = c;

                }

            }

        }

        //fails for swatisingh should display s and i both

        Console.WriteLine(value);

    }

}