#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int test(string a,string s){
    s += a;
    sort(s.begin(),s.end());
    bool o = false;
    for(int i = 0;i < 13;i++){
        string b = "abcdefghijklm";
        b += b[i];
        sort(b.begin(),b.end());
        if(s == b){
            o = true;
            break;
        }
    }
    if(o)return 1;
    else return 0;
}
int main() {
    string s,ans = "";
    cin >> s;
    if(test("a",s))ans += "a\n";
    if(test("b",s))ans += "b\n";
    if(test("c",s))ans += "c\n";
    if(test("d",s))ans += "d\n";
    if(test("e",s))ans += "e\n";
    if(test("f",s))ans += "f\n";
    if(test("g",s))ans += "g\n";
    if(test("h",s))ans += "h\n";
    if(test("i",s))ans += "i\n";
    if(test("j",s))ans += "j\n";
    if(test("k",s))ans += "k\n";
    if(test("l",s))ans += "l\n";
    if(test("m",s))ans += "m\n";
    if(ans == "")ans = "Impossible\n";
    cout << ans;
    return 0;
}