//#include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

/*
#include "boost/multiprecision/cpp_int.hpp"
#include "boost/multiprecision/cpp_dec_float.hpp"
namespace mp = boost::multiprecision;
typedef mp::cpp_int LL;
typedef mp::number<mp::cpp_dec_float<1024>> DD;// 仮数部が1024ビットの浮動小数点数型(TLEしたら小さくする)
*/
 
typedef long double dd;
#define i_7 (ll)(1E9+7)
//#define i_7 998244353
#define i_5 i_7-2
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    return c+i_7;
}
typedef pair<ll,ll> l_l;
typedef pair<dd,dd> d_d;
ll inf=(ll)1E16;
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define rrep(i,r,l) for(ll i=r;i>=l;i--)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}
void Max(ll &pos,ll val){pos=max(pos,val);}//Max(dp[n],dp[n-1]);
void Min(ll &pos,ll val){pos=min(pos,val);}
void Add(ll &pos,ll val){pos=mod(pos+val);}
dd EPS=1E-9;
#define fastio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fi first
#define se second
//#define endl "\n"  //インタラクティブで消す！！！！！！！！！！！！！！！！！！！！！
#define SORT(v) sort(v.begin(),v.end())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
#define POSL(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define POSU(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
template<class T,class S>
inline bool chmax(T &a, S b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
template<class T,class S>
inline bool chmin(T &a, S b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}

void mod_print(ll k){
    ll P=50000;
    rep(y,1,P){
        ll x=mod(y*k);
        
        if(abs(x)<=P||x+P>=i_7){
            if(x+P>=i_7){
                x-=i_7;
            }
            cout<<x<<"/"<<y<<endl;
            //cout<<setprecision(5)<<(dd)x/(dd)y;
            return;
        }
    }
    cout<<"nun"<<endl;
}
#define all(c) c.begin(),c.end()
typedef vector<ll> vl;
//////////////////////////

int main(){fastio
    ll n;cin>>n;
    ll a[n],b[n];
    rep(i,0,n-1)cin>>a[i];
    rep(i,0,n-1)cin>>b[i];
    ll sa=0,sb=0;
    rep(i,0,n-1)sa+=a[i];
    rep(i,0,n-1)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)%(n-2)!=0){
        cout<<-1<<endl;return 0;
    }
    if(sa<sb){
        cout<<-1<<endl;return 0;
    }
    ll kai=(sa-sb)/(n-2);
    ll c[n];
    rep(i,0,n-1){
        c[i]=a[i]-b[i]-kai;
    }
    //rep(i,0,n-1)cout<<c[i]<<" ";cout<<endl;
    rep(i,0,n-1){
        if(c[i]>0||c[i]<-2*kai||c[i]%2==1){
            cout<<-1<<endl;return 0;
        }
    }
    cout<<kai<<endl;
    
    return 0;
}