#include <iostream>
#include <string>

using namespace std;

int main()
{   
    string str;
    getline(cin,str);
    int count[26] = {0};

    for(char ch : str)  count[ch - 'a']++;

    int maxIndex = 0;
    for(int i = 0; i < 26; i++)
    {
        if(count[i] > count[maxIndex])
        {
            maxIndex = i;
        }
    }

    char maxChar = 'a' + maxIndex;
    cout << maxChar;

    return 0;
}