/* Problem URL: https://cses.fi/problemset/task/1743 */

#include <bits/stdc++.h>

using namespace std;

#define V vector

#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)

#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)

#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()

using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;

using ll = long long;

using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;

template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
    os << vec[0];
    for (size_t i = 1; i < vec.size(); i++) {
        os << ' ' << vec[i];
    }
    os << '\n';
    return os;
}

template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
    for (auto &i : vec) {
        is >> i;
    }
    return is;
}

template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
    for (auto &i : vec) {
        os << i[0];
        for (size_t j = 1; j < i.size(); j++) {
            os << ' ' << i[j];
        }
        os << '\n';
    }
    return os;
}

template<class v>
auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
    for (auto &i : vec) {
        for (auto &j : i) {
            is >> j;
        }
    }
    return is;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string fds;
    cin >> fds;

    vi count(26);
    repv(i, fds) {
        count[i - 'A']++;
    }

    string ans(fds.size(), ' ');
    rep(i, ans.size()) {
        int now = -1;
        auto valid = [&](int act){
            int maximal = 0;
            int size = 0;

            rep(i, 26) {
                if (i == act) {
                    rmax(maximal, count[i] - 1);
                    size += count[i] - 1;
                } else {
                    rmax(maximal, count[i]);
                    size += count[i];
                }
            }
            
            return maximal <= size - maximal + 1;
        };
        rep(j, 26) {
            if (count[j] != 0 && (i == 0 || j + 'A' != ans[i - 1]) && valid(j)) {
                now = j;
                count[j]--;
                break;
            }
        }

        if (now == -1) {
            cout << "-1\n";
            return 0;
        }

        ans[i] = now + 'A';
    }
    cout << ans << '\n';
}