import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for k in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for k in range(c)] for k in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10**9)
INF = 10**19
MOD = 10**9 + 7
EPS = 10**-10

N = INT()
A = LIST()
B = LIST()

AB = [0] * N
for i in range(N):
    AB[i] = A[i] - B[i]

if N == 2:
    if A[0]-A[1] != B[1]-B[0]:
        print(-1)
    else:
        if abs(A[0]-A[1]) % 2 == 0:
            ans = abs(A[0]-A[1]) // 2
            print(ans)
        else:
            print(-1)
else:
    if sum(AB) % (N-2) != 0:
        print(-1)
    else:
        if sum(AB) > 0:
            need = 0
            for i in range(N):
                if AB[i] < 0:
                    need += -AB[i]
            ok = 1
            for i in range(N):
                if AB[i] >= 0 and AB[i] < need:
                    ok = 0
            if ok:
                print(sum(AB)//2)
            else:
                print(-1)
        else:
            print(sum(AB)//2)