#include <iostream>
#include <string>
#include <cmath>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <utility>
#include <functional>

using namespace std;

int main() {
	string s;
	int cnt[26] = { 0 };

	cin >> s;
	for (int i = 0; i < 13; ++i) {
		cnt[s[i] - 'a']++;
		if (cnt[s[i] - 'a'] > 2) {
			cout << "Impossible" << endl;
			return 0;
		}
	}
	int c = 0;
	for (int i = 0; i < 13; ++i) {
		if (cnt[i] == 0) {
			c++;
		}
	}
	if (c > 1) {
		cout << "Impossible" << endl;
		return 0;
	}

	for (int i = 0; i < 13; ++i) {
		if (cnt[i] == 0) {
			cout << (char)(i + 'a') << endl;
			return 0;
		}
	}
	for (int i = 0; i < 13; ++i) {
		cout << (char)(i + 'a') << endl;
	}

	return 0;
}