1050 String Subtraction (20分) Given two strings S1 and S2, S=S1-S2 is defined to be the remaining string after taking all the characters in S2 from S1. Your task is simply to calculate S1-S2 for any given strings. However, it might not be that simple to do it fast.
Input Specification: Each input file contains one test case. Each case consists of two lines which gives S1 and S2, respectively. The string lengths of both strings are no more than 10^4. It is guaranteed that all the characters are visible ASCII codes and white space, and a new line character signals the end of a string.
Output Specification: For each test case, print S1-S2 in one line.