using System;
using System.Linq;

public class P0224 {
    public static void Main() {
        var n = int.Parse(Console.ReadLine().Trim());
        var s = Console.ReadLine().Trim();
        var t = Console.ReadLine().Trim();
        Console.WriteLine(s.ToCharArray().Zip(t.ToCharArray(), (i, j) => new { left = i, right = j }).Where(pair => pair.left != pair.right).Count());
    }
}