n=int(input())
a=list(map(int,input().split()))
b=list(map(int,input().split()))

sabun=0
for x in range(n):
    c=b[x]-a[x]
    ans+=c
    
if n==2:
    if a[0]-b[0]==-1*(a[1]-b[0]):
        print(abs(a[0]-b[0]))
    else:
        print(-1)
        
else:
    if ans%(2-n)==0:
        print(ans//(2-n))
    else:
        print(-1)