#include "bits/stdc++.h"
using namespace std;
using Graph = vector<vector<int>>;
typedef long long ll;
typedef pair<ll, ll> P;
#define rep(i,n) for (ll i = 0; i < (n); ++i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const long long mod = 1e9 + 7;

ll gcd(ll a, ll b) {
	return b ? gcd(b, a % b) : a;
}

ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}

ll powMod(ll n, ll k, ll m) {
	if (k == 0) {
		return 1;
	} else if (k % 2 == 1) {
		return powMod(n, k - 1, m) * n % m;
	} else {
		ll t = powMod(n, k / 2, m);
		return t * t % m;
	}
}

int main() {
	string s;
	cin >> s;
	
	vector<ll> v(13);
	
	rep(i, s.size()) {
		ll n = s[i]-'a';
		v[n]++;
	}
	
	vector<char> vc;
	ll cnt=0;;

	rep(i, v.size()) {
		if (v[i] == 0) {
			vc.push_back((char)(i+'a'));
		} else if (v[i] > 2) {
			cout << "Impossible" << endl;
			return 0;
		} else if (v[i] == 2) {
			cnt++;
		}
	}

	if (cnt > 1) {
		cout << "Impossible" << endl;
		return 0;
	}

	if (vc.size() == 0) {
		rep(i, 13) {
			cout << (char)('a'+i) << endl;
		}
	} else {
		rep(i, vc.size()) {
			cout << vc[i] << endl;
		}
	}
}