#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

void solve(ll t) {
	string s;
	
	cin >> s;
	vector<int> v(26);
	for (int i = 0; i < s.length(); i++) {
		v[s[i] - 'a']++;
	}
	
	for (int i = 0; i < 26; i++) {
		if (v[i] > s.length() / 2) {
			cout << "Case #" << i << ": IMPOSSIBLE" << endl;
			return;
		}
	}
	string ans;
	for (int i = 0; i < s.length(); i++) {
		for (int j = 0; j < 26; j++) {
			if (v[j] > 0 and s[i] - 'a' != j) {
				string k {'a' + j};
				ans += k;
				v[j]--;
				break;
			}
		}
	}
	cout << "Case #" << t << ": " << ans << endl;
}


int main() {
	ll t;
	cin >> t;
	
	for (int i = 1; i <= t; i++) {
		solve(i);
	}
	return 0;
}