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 mut diffs: Vec<isize> = b.iter().zip(a.iter())
        .map(|ba| *ba.0 - *ba.1)
        .collect();
    diffs.sort();
    let mut count: isize = diffs[0] / -1isize;
    let result = count;
    for val in (1..n).map(|i| diffs[i]) {
        count -= (val - diffs[0]) / 2isize;
    }
    println!("{}", if count == 0isize { result } else { -1isize });
}