// Arup Guha
// 11/3/2018
// Solution to 2018 SER D1/D2 Problem: Exam

import java.util.*;

public class exam {
	
	public static void main(String[] args) {
		
		// Read in the input.
		Scanner stdin = new Scanner(System.in);
		int cor = stdin.nextInt();
		char[] me = stdin.next().toCharArray();
		char[] you = stdin.next().toCharArray();
		
		// # of questions.
		int n = me.length;
		
		// Count the matches.
		int same = 0;
		for (int i=0; i<me.length; i++) 
			if (me[i] == you[i])
				same++;
		
		// Here we get cor of the same ones and all of the others.
		if (cor <= same) 
			System.out.println(cor + n - same);
		
		// Here we get all of the same ones and the ones that your friend didn't get that were different.
		else 
			System.out.println(same + (n-cor) );	
	}
}