n = int(input()) a = list(map(int, input().split())) b = list(map(int, input().split())) if n == 2: v = abs(a[0] - b[0]) if sum(a) != sum(b): print(-1) else: print(v) elif sum(a) < sum(b): print(-1) elif (sum(a) - sum(b)) % (n - 2) != 0: print(-1) else: v = (sum(a) - sum(b)) // (n - 2) l = [] flag = False for i in range(n): l.append(b[i] - (a[i] - v)) if l[i] % 2 == 1: flag == True if sum(l) != 2 * v or flag: print(-1) else: print(v)