#include<bits/stdc++.h>
using namespace std;
char max_freq_char(string s){
    map<char,int>mp;
    int i, len=s.size();
    for(i=0; i<len; i++)
    {
        mp[s[i]]++;
    }
    int res = -1;
    char ans;
    for(auto x : mp)
    {
        if(res < x.second)
        {
            res = x.second;
            ans = x.first;
        }
    }
    return ans;
}
int main()
{
    string s;
    cin >> s;
    cout<<max_freq_char(s)<<"\n";
}