fn main() {
    let mut temp = String::new();
    std::io::stdin().read_line(&mut temp).ok();
    let temp: Vec<isize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let b0 = temp[0];
    let c0 = temp[1];
    let mut temp = String::new();
    std::io::stdin().read_line(&mut temp).ok();
    let temp: Vec<isize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let b1 = temp[0];
    let c1 = temp[1];

    for i in 0..=b0*b1 {
        let c0 = (b0 * c0.abs() + c0) % b0;
        let c1 = (b1 * c1.abs() + c1) % b1;
        if i % b0 == c0 && i % b1 == c1 {
            println!("{}", i);
            return;
        }
    }
    println!("NaN");
}