import sys
input = sys.stdin.readline

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

if N==2:
    if sum(A)!=sum(B):
        print(-1)
    else:
        print(abs(A[0]-B[0]))

else:
    X=sum(A)-sum(B)

    if X<0:
        print(-1)
        
    elif X%(N-2)!=0:
        print(-1)

    else:
        ANS=X//(N-2)

        A2=[a-ANS for a in A]

        for i in range(N):
            if (B[i]-A2[i])%2!=0 or B[i]-A2[i]<0:
                print(-1)
                break
        else:
            print(ANS)