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

    let diffs: Vec<isize> = b.iter().zip(a.iter())
        .map(|ba| *ba.0 - *ba.1)
        .collect();
    let count: isize = -1isize * diffs.iter().sum::<isize>();
    let diffmax = diffs.iter().max().unwrap();
    let diffmin = diffs.iter().min().unwrap();
    if (n == 2 && count == 0isize) || (n > 2 && count % (n as isize - 2isize) == 0) {
        let count = if n > 2 { count / (n as isize - 2isize) } else { 0isize } ;
        if n == 2 {
            println!("{}", diffs[0].abs());
        } else if diffmin.abs() <= count && diffmax.abs() <= count {
            println!("{}", count);
        } else {
            println!("-1");
        }
    } else {
        println!("-1");
    }
}