import sys
input=sys.stdin.readline

N=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))

if N==2:
    if sum(A)==sum(B):
        print(abs(A[0]-B[0]))
    else:
        print(-1)
    exit()

D=[B[i]-A[i] for i in range(N)]
X=-sum(D)

for d in D:
    y=X+(N-2)*d
    if not(y>=0 and y%(2*(N-2))==0):
        print(-1)
        exit()

print(X//(N-2))