#include <bits/stdc++.h>

#define show(x) cerr << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz=" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = 1e9 + 7;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;

int cnt[26];
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    string s;
    cin >> s;

    int ignore = 0;
    for (const char c : s) {
        cnt[c - 'a']++;
        if (c > 'm') {
            ignore++;
        }
    }
    if (ignore > 0) {
        cout << "Impossible" << endl;
        return 0;
    }

    bool flag = false;
    for (int i = 0; i <= 'm' - 'a'; i++) {
        cnt[i]++;
        bool ok = true;
        for (int j = 0; j <= 'm' - 'a'; j++) {
            if (cnt[j] == 0) {
                ok = false;
                break;
            }
        }
        cnt[i]--;
        if (ok) {
            flag = true;
            cout << (char)(i + 'a') << endl;
        }
    }
    if (not flag) {
        cout << "Impossible" << endl;
    }

    return 0;
}