#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)
using ll = long long;
#define all(p) p.begin(),p.end()

int main(){
	int N;
	cin>>N;
	vector<ll> A(N),B(N);
	rep(i,0,N) cin>>A[i];
	rep(i,0,N) cin>>B[i];
	if(N==2){
		if(A[0]+A[1]==B[0]+B[1]){
			cout<<abs(A[0]-B[0])<<"\n";
		}
		else{
			cout<<"-1\n";
		}
	}
	else{
		ll sum=0;
		rep(i,0,N) sum+=A[i];
		rep(i,0,N) sum-=B[i];
		if(sum%(N-2)!=0){
			cout<<"-1\n";
			return 0;
		}
		ll ans=sum/(N-2);
		rep(i,0,N){
			A[i]-=ans;
			if(B[i]<A[i]||(B[i]-A[i])%2!=0){
				cout<<"-1\n";
				return 0;
			}
		}
		cout<<ans<<"\n";
	}
}