use std::io;
use std::str::FromStr;

fn main() {
    let stdin = io::stdin();
    let mut buf = String::new();
    stdin.read_line(&mut buf).ok();

    let mut it = buf.split_whitespace().map(|n| usize::from_str(n).unwrap());
    let n = it.next().unwrap();

    let mut buf = String::new();
    stdin.read_line(&mut buf).ok();

    let mut it = buf.split_whitespace().map(|n| String::from_str(n).unwrap());
    let s = it.next().unwrap();


    let mut buf = String::new();
    stdin.read_line(&mut buf).ok();

    let mut it = buf.split_whitespace().map(|n| String::from_str(n).unwrap());
    let t = it.next().unwrap();

    let mut ans = 0;
    for i in 0..n {
        if s.chars().nth(i).unwrap() != t.chars().nth(i).unwrap() {
            ans += 1;
        }
    }

    println!("{}", ans);
}