#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<bitset>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<deque>
#include<list>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<functional>
#include<cstdio>
#include<cstdlib>
using namespace std;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define INF 2e9
#define MOD 1000000007
//#define MOD 998244353
#define LINF (long long)4e18
#define jck 3.141592

const double EPS = 1e-10;

using ll = long long;
using Pi = pair<int,int>;
using Pl = pair<ll,ll>;



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