You are given two binary strings A and B of equal length. You have a type of opertion in which you can swap any two elements of string B. Your task is to find the minimum number of operations required to convert string B into string A. If it is not possible, print -1.

Input Format:

First line contains string A.

Second line contains string B.

Output Format:

Print the minimum number of operations required to convert string B into string A. If it is not possible, print -1.

Constraints:

$|A| = |B| ; |S| \; refers \; to \; length \; of \; string \; S$

$1 \le |A| \le 10^5$