#include #include #include #include #include #include #define ALL(x) (x).begin(),(x).end() #define RALL(x) (x).rbegin(),(x).rend() #define REP(i,a,n) for(int i = (a);i < (n);i++) #define PI 3.14159265359 #define MOD 1000000007 using namespace std; int main(){ string s,b = "abcdefghijklm"; cin >> s; vector a(13); int m = 0; REP(i, 0, 13){ int index = s[i]-'a'; if(index > 13)index = 0; a[index]++; m = max(m,a[index]); } if(m > 2)cout << "Impossible\n"; else if(m == 2){ REP(i, 0, 13){ if(a[i] == 0)cout << b[i] << endl; } } else { REP(i, 0, 13){ cout << b[i] << endl; } } return 0; }