#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MOD = 1000000007;
using P = pair<int,int>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()

int main(){
    string s;
    cin >> s;
    vector<int> cnt(8,0);
    int n = s.size();
    rep(i,n){
        cnt[1]++;
        cnt[s[i]-'A'+2]++;
    }
    int x = *max_element(all(cnt));
    rep(i,8) if(cnt[i]==x) cout << i << endl;
    return 0;
}