import sys
input = sys.stdin.readline

N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
C = [B[i]-A[i] for i in range(N)]
D = []

for i in range(1, N):
    if (C[0]-C[i])%2==1:
        print(-1)
        exit()
    
    D.append((C[0]-C[i])//2)

S = sum(D)

if (S-C[0])%(N-2)!=0:
    print(-1)
    exit()

x = (S-C[0])//(N-2)
ans = x

for Di in D:
    ans += x-Di

print(ans)