import sys

# sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
# md = 998244353
md = 10**9+7

def solve(aa, bb):
    sa = sum(aa)
    sb = sum(bb)
    if n == 2:
        if sa == sb:
            return abs(aa[0]-bb[0])
        return -1
    if sa < sb or (sa-sb)%(n-2): return -1
    ans = k = (sa-sb)//(n-2)
    aa = [a-k for a in aa]
    for a, b in zip(aa, bb):
        if b-a < 0 or (b-a) & 1: return -1
        k -= (b-a)//2
        if k < 0: return -1
    return ans

n = II()
aa = LI()
bb = LI()
print(solve(aa,bb))