fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s: Vec<usize> = s.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let mut t = String::new();
    std::io::stdin().read_line(&mut t).ok();
    let t: Vec<usize> = t.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let s1 = s.iter().filter(|&&v| v == 1).count();
    let t1 = t.iter().filter(|&&v| v == 1).count();
    let mut result = vec![vec![0; n]; n];
    for i in 0..n {
        if s[i] == 2 {
            for j in 0..n {
                result[i][j] = 1;
            }
        }
        if t[i] == 2 {
            for j in 0..n {
                result[j][i] = 1;
            }
        }
    }
    let summary = result.iter().map(|v| v.iter().sum::<usize>()).sum::<usize>();
    let s_has_2 = s.iter().filter(|&&v| v == 2).count() > 0;
    let t_has_2 = t.iter().filter(|&&v| v == 2).count() > 0;
    if s_has_2 && t_has_2 {
        println!("{}", summary);
    } else if s_has_2 {
        println!("{}", summary + s1);
    } else if t_has_2 {
        println!("{}", summary + t1);
    } else {
        println!("{}", s1.max(t1));
    }
}