#include <bits/stdc++.h>

using namespace std;
#define int long long
const int MOD = 1000000007;

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N;
	cin >> N;
	vector<int> A(N);
	vector<int> B(N);
	int sumA = 0;
	int sumB = 0;
	for (int i = 0; i < N; i++) {
		cin >> A[i];
		sumA += A[i];
	}
	for (int i = 0; i < N; i++) {
		cin >> B[i];
		sumB += B[i];
	}
	if (N == 2) {
		if (sumA != sumB) {
			cout << -1 << endl;
		} else {
			cout << abs(A[0] - B[0]) << endl;
		}
	} else {
		bool ok = true;
		if (sumA < sumB) {
			ok = false;
		} else {
			int k = sumA - sumB;
			if (k % (N - 2) != 0) {
				ok = false;
			} else {
				int tot = k / (N - 2);
				int c = 0;
				for (int i = 0; i < N; i++) {
					int t = (B[i] - A[i] + tot);
					if (t < 0 || t % 2 != 0) {
						ok = false;
					}
					int x = t / 2;
					A[i] += x - (tot - x);
					c += x;
				}
				if (c != tot) {
					ok = false;
				}
				
				if (ok) {
					cout << tot << endl;
					return 0;
				}
			}
		}
		if (!ok) {
			cout << -1 << endl;
		}
	}
}