#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={0,1,-1,0,1,1,-1,-1,0};
const ll dx[9]={1,0,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

int main(){
    ll n;cin >> n;
    vl a(n),b(n);
    rep(i,n)cin >> a[i];
    rep(i,n)cin >> b[i];
    if(n==2){
        if(a[0]+a[1]==b[0]+b[1]){
            cout << abs(a[0]-b[0]) << endl;
        }
        else cout << -1 << endl;
        return 0;
    }
    ll p=0;rep(i,n)p+=a[i]-b[i];
    if(p<0||p%(n-2)){
        cout << -1 << endl;return 0;
    }
    p/=(n-2);
    rep(i,n)a[i]-=p;
    bool ok=true;
    rep(i,n){
        ll q=b[i]-a[i];
        if(q<0||q%2)ok=false;
    }
    if(ok)cout << p << endl;
    else cout << -1 << endl;
}