#include <algorithm>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <math.h>
using namespace std;
#define int long long

signed main() {
	
	string s;
	cin >> s;
	int cnt[13];
	for (int i = 0; i < 13; i++) {
		cnt[i] = 0;
	}
	bool f = true;
	for (int i = 0; i < 13; i++) {
		if ((int)(s[i] - 'a') < 13) {
			cnt[(int)(s[i] - 'a')]++;
		}else{
			f = false;
		}
	}
	int c = 0;
	for (int i = 0; i < 13; i++) {
		if (cnt[i] == 3) {
			f = true;
		}
		if (cnt[i] == 0) {
			c++;
		}
	}
	if (!f || (c >= 2)) {
		cout << "Impossible" << endl;
	}
	else {
		int x = -1;
		for (int i = 0; i < 13; i++) {
			if (cnt[i] == 0) {
				x = i;
			}
		}
		if (x == -1) {
			for (int i = 0; i < 13; i++) {
				cout << (char)('a' + i) << endl;
			}
		}
		else {
			cout << (char)('a' + x) << endl;
		}
	}
	return 0;
}