Binary Swap
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## Algorithms, String Manipulation

Problem
Editorial
Analytics

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:

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

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

SAMPLE INPUT
1110
1101

SAMPLE OUTPUT
1

Explanation

You can swap the last and second last element in the string B. After swapping string B will become 1110. Therefore, only one operation is required to convert string B into string A.

Time Limit: 1.0 sec(s) for each input file.
Memory Limit: 256 MB
Source Limit: 1024 KB

## This Problem was Asked in

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