You are given two binary strings $A$ and $B$ and are required to make $A$ equals to $B$. There are two types of operations:

1. Swap any two adjacent bits or characters in string $A$. The cost of this operation is 1 unit.
2. Flip the bit or character of the string. The cost of this operation is 1 unit.

What is the minimum cost to make string $A$ equal to $B$?

Input format

• The first line contains one integer that denotes the length of both strings.
• The next two lines take two strings $A$ and $B$ of length $n$ as an input.

Output format

Print one integer that represents the minimum cost required to convert string $A$ to string $B$.

Constraints

$1 \le n \le 10^{5}$

Note

The length of both the strings $A$ and $B$ is always the same.