using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    public void Solve()
    {
        int n = int.Parse(Console.ReadLine());
        char[] S = Console.ReadLine().ToArray();
        char[] T = Console.ReadLine().ToArray();

        int idx = 0;
        int ans = 0;
        while (new string(S) != new string(T))
        {
            if (S[idx] != T[idx])
            {
                S[idx] = T[idx];
                ans++;
            }
            idx++;
        }
        Console.WriteLine(ans);
    }

    static void Main()
    {
        var solver = new Program();
        solver.Solve();
    }
}