N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
if A==B:
  print(0)
  exit()
if N==2:
  if sum(A)!=sum(B):
    print(-1)
  else:
    print(abs(A[0]-B[0]))
  exit()
X=sum(A)-sum(B)
if X<=0 or X%(N-2):
  print(-1)
  exit()
X//=N-2
for i in range(N):
  A[i]-=X
P=0
for i in range(N):
  if A[i]>B[i] or (B[i]-A[i])&1:
    print(-1)
    exit()
  P+=(B[i]-A[i])//2
print(P)