fn gcd(a: usize, b: usize) -> usize {
    if b == 0 { return a; }
    gcd(b, a%b)
}

fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nm[0];
    let m = nm[1];
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let mut b = String::new();
    std::io::stdin().read_line(&mut b).ok();
    let b: Vec<usize> = b.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let gcdval = gcd(n, m);
    for i in 0..n*m/gcdval {
        if a[i%n] == b[i%m] {
            println!("{}", i+1);
            return;
        }
    }
    println!("-1");
}