#include <bits/stdc++.h>

using namespace std;

int freq[30];

void addChar(char c) {
    if ('A' <= c && c <= 'Z') c += 'a' - 'A';
    if ('a' <= c && c <= 'z') freq[c - 'a']++;
}

int main() {
    // freopen("in", "r", stdin);
    // freopen("out", "w", stdout);

    int t;
    scanf("%d ", &t);

    while (t--) {
        char s[210];
        fgets(s, 210, stdin);

        memset(freq, 0, sizeof freq);
        for (int i = 0; s[i]; i++) addChar(s[i]);

        int maxi = *max_element(freq, freq + 30);
        for (int i = 0; i < 26; i++) {
            if (freq[i] == maxi) printf("%c", 'a' + i);
        }
        printf("\n");
    }

    return 0;
}