using System;

public class Program {
    public static void Main() {
        int n = int.Parse(Console.ReadLine());
        string line1 = Console.ReadLine();
        string line2 = Console.ReadLine();
        int result = 0;
        for (int i = 0; i < n; i++) {
            if (line1[i] != line2[i]) result++;
        }
        Console.WriteLine(result);
    }
}