fn main() {
    let n: usize = {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        buf.trim_end().parse().unwrap()
    };
    let a: Vec<i64> = {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        let iter = buf.split_whitespace();
        iter.map(|x| x.parse().unwrap()).collect()
    };
    let b: Vec<i64> = {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        let iter = buf.split_whitespace();
        iter.map(|x| x.parse().unwrap()).collect()
    };

    let mut c = vec![0; n];
    for i in 0..n {
        c[i] = a[i] - b[i];
    }
    c.sort();

    let mut sum = 0;
    for i in (0..(n - 1)).rev() {
        c[i] -= sum;
        let x = c[i + 1] - c[i];
        if x % 2 == 0 {
            c[i] = (c[i] + c[i + 1]) / 2;
            sum += x / 2;
        } else {
            println!("-1");
            return;
        }
    }

    if c[0] == 0 {
        println!("{}", sum);
    } else {
        println!("-1");
    }
}