#include<bits/stdc++.h>

using namespace std;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

using ll = long long;
void solve() {
    string s;
    cin >> s;
    int n = s.size();
    for (int len = n; len > 0; --len) {
        map<string, int> last, cnt, ok;
        map<string, int> first;
        for (int i = 0; i + len - 1 < n; ++i) {
            string t(s.begin() + i, s.begin() + i + len);
            if (last.count(t) && last[t] + len - 1 >= i) ok[t] = 1;
            cnt[t]++;
            last[t] = i;
            if (first.count(t) == 0) first[t] = i;
        }
        string mn;
        for (auto [t, x] : cnt) {
            if (x < 2) continue;
            if (ok[t]) continue;
            if (mn.empty() || first[t] < first[mn]) mn = t;
        }
        if (mn.empty()) continue;
        cout << mn << '\n';
        return;
    }
}

int main() {
#ifndef LOCAL
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#else
    freopen("input.txt", "r", stdin);
#endif
    int t;
    cin >> t;
    while (t--)
        solve();
    return 0;
}