use std::io::{self, Read};

fn main() {
    let mut input = String::new();
    io::stdin().read_to_string(&mut input).ok();
    let input = input
        .split_whitespace()
        .map(|s| s.chars().collect::<Vec<_>>())
        .collect::<Vec<_>>();

    let answer = input[1]
        .iter()
        .zip(input[2].iter())
        .filter(|&(c1, c2)| c1 != c2)
        .count();

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