#include <iostream>
#include <algorithm>
#include <cmath>
#define int long long
#define rep(i, n) for(i = 0; i < n; i++)
using namespace std;

int n;
int a[100000];
int b[100000];
int c[100000];

signed main() {
	int i;
	
	cin >> n;
	rep(i, n) cin >> a[i];
	rep(i, n) cin >> b[i];
	
	int sumA = 0;
	rep(i, n) sumA += a[i];
	
	int sumB = 0;
	rep(i, n) sumB += b[i];
	
	//N = 2の解法
	if (n == 2) {
		if (sumA != sumB) {
			cout << -1 << endl;
		}
		else {
			cout << abs(a[0] - b[0]) << endl;
		}
		return 0;
	}
	
	//N >= 3の解法
	if (sumA - sumB < 0 || (sumA - sumB) % (n - 2) != 0) {
		cout << -1 << endl;
		return 0;
	}
	
	int T = (sumA - sumB) / (n - 2);
	int cst = 0;
	rep(i, n) {
		c[i] = a[i] - b[i] - T;
		if (c[i] > 0 || (-c[i]) % 2 == 1) {
			cout << -1 << endl;
			return 0;
		}
		cst += (-c[i]) / 2;
	}
	
	if (cst != T) {
		cout << -1 << endl;
		return 0;
	}
	
	cout << T << endl;
	return 0;
}