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)

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

if F:
    print(H)
else:
    print(-1)