package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := getNextInt(scanner)
	aa := make([]int64, n)
	bb := make([]int64, n)
	cc := make([]int64, n)
	for i := 0; i < n; i++ {
		aa[i] = getNextInt64(scanner)
	}
	for i := 0; i < n; i++ {
		bb[i] = getNextInt64(scanner)
	}
	m := map[int64]int{}
	var sum int64
	for i := 0; i < n; i++ {
		cc[i] = aa[i] - bb[i]
		m[mod(cc[i], 2)]++
		sum += cc[i]
	}
	if len(m) > 1 {
		fmt.Fprintln(writer, -1)
		return
	}
	if sum < 0 {
		fmt.Fprintln(writer, -1)
		return
	}
	if n == 2 {
		if sum != 0 {
			fmt.Fprintln(writer, -1)
			return
		}
		fmt.Fprintln(writer, abs(cc[0]))
		return
	}
	if sum%int64(n-2) != 0 {
		fmt.Fprintln(writer, -1)
		return
	}
	cnt := sum / int64(n-2)
	for i := 0; i < n; i++ {
		aa[i] -= cnt
	}
	var horobiyo int64
	for i := 0; i < n; i++ {
		if aa[i] > bb[i] {
			fmt.Fprintln(writer, -1)
			return
		}
		if (bb[i]-aa[i])%2 == 1 {
			fmt.Fprintln(writer, -1)
			return
		}
		horobiyo += (bb[i] - aa[i]) / 2
	}
	if horobiyo != cnt {
		fmt.Fprintln(writer, -1)
		return
	}
	fmt.Fprintln(writer, cnt)
}

func mod(n, m int64) int64 {
	n %= m
	if n < 0 {
		return n + m
	}
	return n
}
func abs(a int64) int64 {
	if a < 0 {
		return -a
	}
	return a
}