CF169B Replacing Digits

You are given an integer $ a $ that consists of $ n $ digits. You are also given a sequence of digits $ s $ of length $ m $ . The digit in position $ j $ ( $ 1

The first line contains positive integer $ a $ . Its length $ n $ is positive and doesn't exceed $ 10^{5} $ . The second line contains sequence of digits $ s $ . Its length $ m $ is positive and doesn't exceed $ 10^{5} $ . The digits in the sequence $ s $ are written consecutively without any separators. The given number $ a $ doesn't contain leading zeroes.

Print the maximum value that can be obtained from $ a $ after a series of replacements. You are allowed to use not all elements from $ s $ . The printed number shouldn't contain any leading zeroes.