N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
a = sum(A)
b = sum(B)
import sys

if N == 2:
    if a != b:
        print(-1)
        exit()
    else:
        ans = abs(A[0] - B[0])
        print(ans)
        exit()
if a < b:
    print(-1)
    exit()
if (a - b) % (N - 2) != 0:
    print(-1)
    exit()
q = (a - b) // (N - 2)
#print(q)
for a,b in zip(A,B):
    a -= q
    if a > b:
        print(-1)
        exit()
    if (b - a) % 2 != 0:
        print(-1)
        exit()
print(q)