#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD % 1000000007
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


int main() {
	string s;
	cin >> s;
	int a[32] = { 0 };
	REP(i, 13) {
		a[s[i] - 'a']++;
	}
	int cnt = 0;
	REP(i, 32) {
		if (a[i] == 2) cnt++;
	}
	if (cnt == 6) {
		REP(i, 32) {
			if (a[i] == 1) cout << char(i + 'a') << endl;
		}
	}
	else {
		cout << "Impossible" << endl;
	}
}