N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
flg=0
if N==2:
    if sum(A)==sum(B):
        flg=1
        time=abs(A[0]-B[0])
else:
    if (sum(A)-sum(B))%(N-2)==0:
        time=(sum(A)-sum(B))//(N-2)
        flg=1
        for i in range(N):
            if (A[i]-B[i]+time)%2==1 or (B[i]>A[i]-time):
                flg=0
print(time if flg else -1)