use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let s: Vec<char> = itr.next().unwrap().chars().collect();
    let t: Vec<char> = itr.next().unwrap().chars().collect();
    let mut ans = 0;
    for i in 0..n {
        ans += (s[i] != t[i]) as u64;
    }
    println!("{}", ans);
}