import java.io.*;
import java.math.MathContext;
import java.util.*;

public class StrangeTeacher {
    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    private static final PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
    private static StringTokenizer st;

    private static int readInt() throws IOException {
        while (st == null || !st.hasMoreTokens()) st = new StringTokenizer(br.readLine());
        return Integer.parseInt(st.nextToken());
    }

    public static void main(String[] args) throws IOException {
        pw.println(solve());
        pw.close();
    }

    private static long solve() throws IOException {
        int N = readInt();
        long[] A = new long[N];
        for (int i = 0; i < N; i++) A[i] = readInt();
        for (int i = 0; i < N; i++) A[i] -= readInt();

        if (N == 2) {
            if (A[0] + A[1] == 0) return Math.abs(A[0]);
            else return -1;
        }

        long sum = Arrays.stream(A).sum();
        if (sum < 0 || sum % (N - 2) != 0) return -1;
        long operation = sum / (N-2);

        for (int i = 0; i < N; i++) {
            if ((operation - A[i]) % 2 != 0 || operation < A[i] ) return -1;
        }

        return operation;
    }
}