#include <bits/stdc++.h>

using namespace std;

string s, t;

inline int check(int x)
{
	for (int i = 0; t[i] != '\0'; i++) {
		if (s[i + x] != t[i] && s[i + x] != '?') return 0;
	}
	for (int i = 0; t[i] != '\0'; i++) {
		s[i+x] = t[i];
	}
	for (int i = 0; s[i] != '\0'; i++) {
		if (s[i] == '?') s[i] = 'a';
	}
	cout << s << endl;
	return 1;
}

int main()
{
	cin >> s >> t;
	int l = s.length() - 1;
	for (int i = l; i >= 0; i--) {
		if (check(i) == 1) return 0;
	}
	cout << "UNRESTORABLE" << endl;
	return 0;
}