#include #include #include #include #include #include #include #include #include #include using namespace std; #ifdef _WIN32 #include #endif int main() { int p = 0, ans = 0, cnt = 0; string s; cin >> s; vector v(26, 0); for (int i = 0; i < s.size(); i++) v[s[i] - 'a']++; for (int i = 0; i < 26; i++){ if (v[i] == 2) p++; if (v[i] == 1) ans = i; } if (p == 6 && ans) cout << char('a' + ans) << endl; else cout << "Impossible" << endl; }