#include <memory.h>
#include <iostream>
#include <cstdio>
#include <vector>
#include <string>
#include <map>
#include <algorithm>
#include <set>
#include <map>
#include <cassert>
#include <ctime>
#include <cstdlib>
#include <queue>


using namespace std;

typedef long long ll;

const int maxn = 256;

string s;
int n;
char dp[maxn][maxn];
char _can[maxn];
char *can = _can + 1;

bool solve(int start, int len) {
    memset(dp, 0, sizeof(dp));

    for (int i = 0; i + len <= n; i++) {
        bool ok = 1;
        for (int j = 0; j < len; j++) ok &= s[i + j] == s[start + j];
        if (ok) dp[i][i + len - 1] = 1;
    }

    for (int i = n - 1; i >= 0; i--) {
        for (int j = -1; j < n; j++) can[j] = 0;
        can[i - 1] = 1;

        for (int j = i; j < n; j++) {
            if (s[j] == s[(j - i) % len + start]) {
                can[j] |= can[j - 1];
            }
            for (int k = j - len; k >= i - 1; k -= len) {
                can[j] |= can[k] && dp[k + 1][j];
            }
            if ((j - i + 1) % len == 0) {
                dp[i][j] = can[j];
            }
        }
    }
    return dp[0][n - 1];
}

int main() {
    freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);

    cin >> s;
    /*for (int i = 0; i < 192; i++) s += 'a';
    vector<int> p(192);
    for (int i = 0; i < 192; i++) p[i] = i;
    random_shuffle(p.begin(), p.end());
    for (int i = 0; i < 192 / 2; i++) s[p[i]] = 'b';*/

    n = s.length();

    vector<int> cnt(26);
    for (int i = 0; i < n; i++) cnt[s[i] - 'a']++;

    for (int len = 1; len <= n; len++) if (n % len == 0) {
        set<string> st;
        for (int i = 0; i + len <= n; i++) {
            string cur = "";
            bool ok = 1;
            ok &= s[i] == s[0] && s[i + len - 1] == s[n - 1];
            vector<int> ccnt(26);
            for (int j = 0; j < len; j++) ccnt[s[i + j] - 'a']++;
            for (int j = 0; j < len; j++) cur += s[i + j];
            for (int j = 0; j < 26; j++) ok &= ccnt[j] * (n / len) == cnt[j];

            ok &= st.find(cur) == st.end();
            if (ok) {
                st.insert(cur);
                if (solve(i, len)) {
                    for (int j = 0; j < len; j++) cout << s[i + j];
                    cout << endl;
                    return 0;
                }
            }
        }
    }

    return 0;
}