String Subtraction (20)

输入描述:

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 104.  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.

输出描述:

For each test case, print S1 - S2 in one line.