#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;

template<typename T1,typename T2>
ostream &operator<<(ostream &os,const pair<T1,T2>&p){
    os<<p.first<<" "<<p.second;
    return os;
}

template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==v.size()?"":" ");
    return os;
}


signed main(){
    int n;cin>>n;
    vector<ll> a(n),b(n),d(n);
    rep(i,n) cin>>a[i];
    rep(i,n) cin>>b[i];
    rep(i,n) d[i]=a[i]-b[i];
    ll ds=0;
    rep(i,n) ds+=d[i];
    if(n==2){
        if(ds==0){
            cout<<abs(d[0])<<endl;
        }else{
            cout<<-1<<endl;
        }
        return 0;
    }

    if(ds<0 or ds%(n-2)){
        cout<<-1<<endl;
        return 0;
    }
    ll cs=ds/(n-2);
    vector<ll> c(n);
    rep(i,n){
        ll t=cs-d[i];
        if(t<0 or t%2){
            cout<<-1<<endl;
            return 0;
        }
        c[i]=t/2;
    }
    ll s=0;
    rep(i,n)s+=c[i];
    if(cs!=s){
        cout<<-1<<endl;
        return 0;
    }
    cout<<s<<endl;
    return 0;
}