import java.io.*;

class Process {
    private String S;
    private String T;

    Process(String S, String T) {
        this.S = S;
        this.T = T;
    }

    int getResult() {
        int count = 0;
        for(int i = 0; i < S.length(); i++) {
            if(S.charAt(i) != T.charAt(i)) {
                count++;
            }
        }

        return count;
    }
}

public class Main {
    public static void main(String[] args) throws IOException {
        var bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        var printWriter    = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));

        // 入力
        int n = Integer.parseInt(bufferedReader.readLine().trim());

        String S = bufferedReader.readLine().trim();

        String T = bufferedReader.readLine().trim();

        // 処理および出力
        printWriter.println((new Process(S, T)).getResult());
        
        bufferedReader.close();
        printWriter.close();
    }
}