#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <unordered_map>


int main() {

    std::ifstream fin("input.txt");

    std::string str1, str2;

    fin >> str1 >> str2;

    std::unordered_map<char, int> abc;

    for (char ch : str1) {
        abc[ch]++;
    }

    for (char ch : str2) {
        if (abc[ch] == 0) {
            std::cout << ch;
            break;
        }
        abc[ch]--;
    }
}