use std::io::Read;

fn read<T: std::str::FromStr>() -> T {
    let token: String = std::io::stdin()
        .bytes()
        .map(|c| c.ok().unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}

fn main() {
    let n: i32 = read();
    let a: Vec<i32> = (0..n).map(|_| read()).collect();
    let b: Vec<i32> = (0..n).map(|_| read()).collect();
    let d = a.iter().sum::<i32>() - b.iter().sum::<i32>();
    if n == 2 {
        if d == 0 {
            println!("{}", (a[0] - b[0]).abs());
        } else {
            println!("-1");
        }
        return;
    }
    if d < 0 || d % (n - 2) != 0 {
        println!("-1");
        return;
    }
    let k = d / (n - 2);
    let a2: Vec<i32> = a.iter().map(|x| x - k).collect();
    let mut m = 0;
    for (a, b) in a2.iter().zip(b.iter()) {
        if a > b {
            println!("-1");
            return;
        }
        m += (b - a) / 2;
    }
    if m <= k {
        println!("{}", k);
    } else {
        println!("-1");
    }
}