import sys
from heapq import heapify, heappush, heappop

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()

smA = sum(A)
smB = sum(B)
if N == 2:
    if smA != smB:
        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 smA < smB:
        print(-1)
    else:
        if (smA-smB) % (N-2) == 0:
            limit = (smA-smB) // (N-2)
            que  = [0] * N
            for i in range(N):
                que[i] = A[i] - B[i]
            heapify(que)
            cnt = 0
            while que:
                cur = heappop(que)
                if cur > INF:
                    print(-1)
                    exit()
                nxt = cur - cnt
                if nxt < 0:
                    cnt += -nxt
                    cur = -nxt 
                    heappush(que, cur)
                else:
                    heappush(que, cur)
                    break
            if sum(que) % (N-2) == 0:
                if (sum(que)-cnt*N) // (N-2) + cnt <= limit:
                    ans = (sum(que)-cnt*N) // (N-2) + cnt
                    print(ans)
                else:
                    print(-1)
            else:
                raise Exception
        else:
            print(-1)