N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
for i in range(N):
    A[i] -= B[i]
suma = sum(A)
if N == 2:
    if suma != 0:
        print(-1)
    else:
        print(abs(B[i]))
    exit()
if suma % (N - 2) != 0:
    print(-1)
    exit()
tot = suma // (N-2)
if max(A) > tot:
    print(-1)
    exit()
ans = 0
for i in range(N):
    if (tot - A[i]) % 2 != 0:
        print(-1)
        exit()
print(tot)