import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		int N = 0;
		InputStreamReader is = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(is);
        String X1 = br.readLine();
       	String X2 = br.readLine();
       	String X3 = br.readLine();
       	int C = Integer.parseInt(X1);
       	char n[] = X2.toCharArray();
       	char m[] = X3.toCharArray();
       	
       	for(int i=0;(C-1)>=i;i++){
       		if(n[i]!=m[i]){
       			N = N + 1;
       		}
       	}
       	System.out.println(N);
	}
}