import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] sa = br.readLine().split(" ");
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sa[i]);
		}
		sa = br.readLine().split(" ");
		int[] b = new int[n];
		for (int i = 0; i < n; i++) {
			b[i] = Integer.parseInt(sa[i]);
		}
		br.close();

		long sum = 0;
		int[] d = new int[n];
		for (int i = 0; i < n; i++) {
			d[i] = a[i] - b[i];
			sum += d[i];
		}
		if (n == 2) {
			if (sum == 0) {
				System.out.println(Math.abs(d[0]));
			} else {
				System.out.println(-1);
			}
			return;
		}
		if (sum < 0 || sum % (n - 2) != 0) {
			System.out.println(-1);
			return;
		}

		long cnt = sum / (n - 2);
		long sum2 = 0;
		for (int i = 0; i < n; i++) {
			long val = (cnt - d[i]);
			if (val < 0 || val % 2 != 0) {
				System.out.println(-1);
				return;
			}
			sum2 += val / 2;
		}
		if (sum2 == cnt) {
			System.out.println(cnt);
		} else {
			System.out.println(-1);
		}
	}
}