#include<bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
#define vec vector<ll>
#define mat vector<vector<ll> >
#define fi first
#define se second
typedef long long ll;
typedef pair<ll,ll> pll;
typedef long double ld;
const ll inf=1e9+7;
const ll mod=998244353;
signed main(){
    ll n;cin>>n;
    ll s=0;
    vector<ll>a(n);
    vector<ll>b(n);
    rep(i,n){
        cin>>a[i];
        s+=a[i];
    }
    rep(i,n){
        cin>>b[i];
        s-=b[i];
    }
    if(n==2){
        if(s==0){
            cout<<abs(a[0]-b[0])<<endl;
        }else{
            cout<<-1<<endl;
        }
        return 0;
    }
    if(s%(n-2)){
        cout<<-1<<endl;
        return 0;
    }
    ll ma=0;
    bool f=1;
    s/=(n-2);
    rep(i,n){
        ll d=abs(a[i]-b[i]);
        if(d>s)f=0;
        if(s%2!=d%2){
            f=0;
        }
    }
    if(f)cout<<s<<endl;
    else cout<<-1<<endl;
}