using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Magatro
{
    static void Main()
    {
        int cnt = 0;
        int N = int.Parse(Console.ReadLine());
        char[] A, B;
        A = Console.ReadLine().ToArray();
        B = Console.ReadLine().ToArray();
        for(int i = 0; i < N; i++)
        {
            if (A[i] != B[i])
            {
                cnt++;
            }
        }
        Console.WriteLine(cnt);
    } 
}