import numpy as np N=int(input()) A=np.array([int(x) for x in input().split()]) B=np.array([int(x) for x in input().split()]) if N==2: if sum(A) != sum(B): print(-1) else: print(abs(A[0]-B[0])) else: if sum(A)<sum(B) or (sum(A)-sum(B))%(N-2) !=0: print(-1) exit(0) t=(sum(A)-sum(B))//(N-2) A-=t res=t for a,b in zip(A,B): if a>b or (b-a)%2==1: print(-1) exit(0) print(t)