n=int(input())
*a,=map(int,input().split())
*b,=map(int,input().split())
dif=sum(a)-sum(b)

if n==2:
    if dif!=0:
        print(-1)
    else:
        print(abs(a[0]-b[0]))
elif dif>=0 and dif%(n-2)==0:
    x=dif//(n-2)
    for i in range(n):
        if (b[i]-(a[i]-x))%2==1:
            print(-1)
            exit()
    print(x)
else:
    print(-1)