복호화.java

//  복호화

import java.util.*;
import java.lang.*;
import java.io.*;

class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());

        for (int i = 0; i < n; i++) {
            String arr = br.readLine();
            Map<Character, Integer> charCount = new HashMap<>();
            for (int j = 0; j < arr.length(); j++) {
                char c = arr.charAt(j);
                if (c != ' ') { // Ignore spaces
                    charCount.put(c, charCount.getOrDefault(c, 0) + 1);
                }
            }

            List<Map.Entry<Character, Integer>> entryList = new ArrayList<>(charCount.entrySet());
            entryList.sort((a, b) -> {
                if (b.getValue().equals(a.getValue())) {
                    return Character.compare(a.getKey(), b.getKey());
                }
                return b.getValue() - a.getValue();
            });

            if (entryList.size() != 1 && entryList.get(0).getValue().equals(entryList.get(1).getValue())) {
                System.out.println("?");
            } else {
                System.out.println(entryList.get(0).getKey());
            }
        }
    }
}