#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main(void) {
	string s;
	cin >> s;
	vector<int> v(13, 0);
	for (int i = 0; i < 13; ++i) {
		++v[s[i] - 'a'];
	}
	int zero = count(v.begin(), v.end(), 0);
	if (zero >= 2) cout << "Impossible" << endl;
	else {
		if (zero == 1) {
			for (int i = 0; i < 13; ++i) {
				if (v[i] == 0)
					cout << (char)(i + 'a') << endl;
			}
		}
		else if (zero == 0) {
			sort(s.begin(), s.end());
			for (int i = 0; i < 13; ++i)
				cout << s[i] << endl;
		}
	}
	return 0;
}