#include using namespace std; #define REP(i,n) for(int i=0; i<(int)(n); i++) #define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++) #define ALL(x) (x).begin(), (x).end() const double PI = acos(-1); int main() { ios_base::sync_with_stdio(0); cin.tie(0); string s; cin >> s; map cnt; for (char c: s) cnt[c]++; if (cnt.size() == 13) { for (char c = 'a'; c <= 'm'; c++) cout << c << endl; } else if (cnt.size() == 12) { for (char c = 'a'; c <= 'm'; c++) if (!cnt[c]) cout << c << endl; } else { cout << "Impossible" << endl; } return 0; }