class Program
{
    static void Main(string[] args)
    {
        string inputLength = Console.ReadLine()!;
        string topWord = Console.ReadLine()!;
        string bottomWord = Console.ReadLine()!;

        List<char> topList = new List<char>();
        List<char> bottomList = new List<char>();

        ListFunc(topList, topWord);
        ListFunc(bottomList, bottomWord);

        int count = 0;
        for (int i = 0; i < topList.Count; i++)
        {
            if (topList[i] != bottomList[i])
            {
                count++;
            }
        }

        Console.WriteLine(count);
    }

    public static void ListFunc(List<char> wordList, string word)
    {
        foreach (char c in word)
        {
            wordList.Add(c);
        }
    }
}