#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <functional>

#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define MOD 1000000007
#define int long long
using ll = long long;
using namespace std;
const int INF = 1LL << 50;
using P = pair<int, int>;

template <class T>
bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    else {
        return false;
    }
}
template <class T>
bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    else {
        return false;
    }
}
struct Setup {
    Setup() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    }
} SETUP;

int calc(int x, int y) {
    return abs(x - y);
}

signed main() {
    string s; cin >> s;
    map<char, int> mp;
    for (auto c : s) {
        mp[c]++;
    }

    int two = 0, one = 0;
    for (auto p : mp) {
        if (p.second == 2) two++;
        else if (p.second == 1) one++;
    }

    if (two == 6 && one == 1) {
        for (auto p : mp) {
            if (p.second == 1) {
                cout << p.first << endl;
            }
        }
    }
    else {
        puts("Impossible");
    }
}