import sys
input=sys.stdin.readline
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    N=I()
    A=LI()
    B=LI()
    
    if N==2:
        a=A[0]-B[0]
        b=A[1]-B[1]
        if a==-b:
            print(abs(a))
        else:
            print(-1)
            
    else:
        diff=0
        M=0
        # 答え候補はすぐわかる
        for i in range(N):
            d=A[i]-B[i]
            diff+=d
            
        if diff%(N-2)!=0:
            print(-1)
        else:
            #全員-1して，誰かを＋2，これがans回
            
            ans=diff//(N-2)
            for i in range(N):
                A[i]-=ans
            
            cnt=0
            for i in range(N):
                if B[i]-A[i]<0:
                    ans=-1
                    break
                elif (B[i]-A[i])%2!=0:
                    ans=-1
                    break
                else:
                    cnt+=(B[i]-A[i])//2
                    
            if cnt==ans:
                print(ans)
            else:
                print(-1)
                    
            
        


main()