#include <iostream>
#include <string>
#include <algorithm>
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
long long a[100010], b[100010];
long long sum = 0, sum1 = 0;
int main() {
	long long n;
	cin >> n;
	for (long long i = 0; i < n; i++) {
		cin >> a[i];
		sum += a[i];
	}
	for (long long i = 0; i < n; i++) {
		cin >> b[i];
		sum1 += b[i];
	}
	if (n == 2) {
		if (sum == sum1) {
			cout << abs(a[0] - b[0]) << endl;
		}
		else {
			cout << "-1" << endl;
		}
		return 0;
	}
	else {
		if ((sum - sum1) % (n - 2) != 0) {
			cout << "-1" << endl;
			return 0;
		}
		long long c = (sum - sum1) / (n - 2);
		long long co = 0;
		if (c < 0) {
			cout << "-1" << endl;
			return 0;
		}
		for (int i = 0; i < n; i++) {
			if ((c - (a[i] - b[i])) % 2 != 0) {
				cout << "-1" << endl;
				return 0;
			}
			co += (c - (a[i] - b[i])) / 2;
		}
		if (c == co) {
			cout << c << endl;
		}
		else {
			cout << "-1" << endl;
		}
	}
	return 0;
}