import numpy as np
N=int(input())
A=np.array([int(x) for x in input().split()])
B=np.array([int(x) for x in input().split()])
if N==2:
    if sum(A) != sum(B):
        print(-1)
    else:
        print(abs(A[0]-B[0]))
else:
    if sum(A)<sum(B) or (sum(A)-sum(B))%(N-2) !=0:
        print(-1)
        exit(0)
    t=(sum(A)-sum(B))//(N-2)
    A-=t
    res=t
    x=B-A
    if np.all((x>=0) & (x%2==0)):
        print(t)
    else:
        print(-1)