Given two strings A and B with the same length and composed of uppercase English letters, ensure that each letter in A and B appears the same number of times.You can exchange two adjacent characters in string A each time, find out how many times you need to exchange so that string A becomes string B.

The first line is a positive integer N \ (2≤N≤10^6), which represents the length of the string.The second and third lines each have a string of length N , which represent sting A and string B and contain only uppercase letters.

A nonnegative integer that represents the minimum number of exchanges.