Little Susie loves strings. Today she calculates distances between them. As Susie is a small girl after all, her strings contain only digits zero and one. She uses the definition of Hamming distance:

We will define the distance between two strings *s* and *t* of the same length consisting of digits zero and one as the number of positions *i*, such that *s*_{i} isn't equal to *t*_{i}.

As besides everything else Susie loves symmetry, she wants to find for two strings *s* and *t* of length *n* such string *p* of length *n*, that the distance from *p* to *s* was equal to the distance from *p* to *t*.

It's time for Susie to go to bed, help her find such string *p* or state that it is impossible.

The first line contains string *s* of length *n*.

The second line contains string *t* of length *n*.

The length of string *n* is within range from 1 to 10^{5}. It is guaranteed that both strings contain only digits zero and one.

提交代码