#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
	int n; cin>>n;
	ll a[100010], b[100010];
	ll sa=0, sb=0;
	for(int i=0; i<n; i++){
		cin>>a[i];
		sa+=a[i];
	}
	for(int i=0; i<n; i++){
		cin>>b[i];
		sb+=b[i];
	}
	if(n==2){
		if(sa==sb){
			cout<<abs(a[0]-b[0])<<endl;
		}else{
			cout<<-1<<endl;
		}
		return 0;
	}
	if(sa<sb || (sa-sb)%(n-2)!=0){
		cout<<-1<<endl;
		return 0;
	}
	ll m=(sa-sb)/(n-2);
	for(int i=0; i<n; i++){
		a[i]-=m;
	}
	for(int i=0; i<n; i++){
		if(a[i]>b[i] || (b[i]-a[i])%2!=0){
			cout<<-1<<endl;
			return 0;
		}
	}
	cout<<m<<endl;
	return 0;
}