N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))

D=[A[i]-B[i] for i in range(N)]
E=sum(D)

if N>=3:
    F=True
    H=0
    M=2*(N-2)
    for i in range(N):
        X=E-(N-2)*D[i]
        if X>=0 and X%M==0:
            H+=X//M
        else:
            F=False

    if F:
        print(H)
    else:
        print(-1)
else:
    if E==0:
        print(abs(A[0]-B[0]))
    else:
        print(-1)