memset(v, -1, sizeof(v));
bool ok = true;
for (int i = 0, sz = a.size(); i < sz; i++) {
	int cur = a[i] - 'A';
	int tar = b[i] - 'A';
	if (v[cur] == -1) {
		v[cur] = tar;
	} else if (v[cur] != tar) {
		ok = false;
		break;
	}
}
for (int i = 0; i < 26; i++) {
	if (v[i] == -1) {
		ok = false;
		break;
	}
	for (int j = 0; j < i; j++) {
		if (v[i] == v[j]) {
			ok = false;
		}
	}
}
if (!ok) {
	cout << "Failed" << endl;
} else {
	for (int i = 0, sz = c.size(); i < sz; i++) {
		cout << char('A' + v[c[i] - 'A']);
	}
	cout << endl;
}