N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
D=[a-b for a,b in zip(A,B)]
if N==2:
    if sum(D)==0:
        ans=0
    else:
        ans=-1
else:
    if sum(D)<0 or sum(D)%(N-2):
        ans=-1
    else:
        cnt=sum(D)//(N-2)
        for i in range(N):
            A[i]-=cnt
        if all(a<=b and b%2==b%2 for a,b in zip(A,B)):
            ans=cnt
        else:
            ans=-1
print(ans)