#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;
use std::ops::Bound::*;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let n = read::<usize>();
    let a = read_vec::<i64>();
    let b = read_vec::<i64>();
    let a = a
        .iter()
        .zip(b.iter())
        .map(|(an, bn)| an - bn)
        .collect::<Vec<_>>();

    if n == 2 {
        if a[0] != -1 * a[1] {
            println!("-1");
            return;
        }
        println!("{}", a[0].abs());
        return;
    }

    if a.iter().sum::<i64>() % (n as i64 - 2) != 0 {
        println!("-1");
        return;
    }

    let cand = a.iter().sum::<i64>() / (n as i64 - 2);
    if cand < 0 {
        println!("-1");
        return;
    }

    let mut cycle = vec![0; n];
    for i in 0..n {
        if (cand - a[i]) % 2 != 0 {
            println!("-1");
            return;
        }
        cycle[i] = (cand - a[i]) / 2;
    }
    if cycle.iter().sum::<i64>() != cand {
        println!("-1");
        return;
    }

    println!("{}", cand);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}