#pragma GCC optimize("O3")
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <cfloat>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <fstream>
#include <functional>
#include <bitset>
using namespace std;

using ll = long long;
using P = pair<int, int>;
using T = tuple<int, int, int>;

template <class T> inline T chmax(T &a, const T b) {return a = (a < b) ? b : a;}
template <class T> inline T chmin(T &a, const T b) {return a = (a > b) ? b : a;}

constexpr int MOD = 1e9 + 7;
constexpr int inf = 1e9;
constexpr long long INF = 1e18;

#define all(a) (a).begin(), (a).end()

int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n; cin>>n;
    vector<ll> a(n), b(n);
    for(int i=0; i<n; i++) cin>>a[i];
    for(int i=0; i<n; i++) cin>>b[i];

    ll asum = accumulate(all(a), 0LL);
    ll bsum = accumulate(all(b), 0LL);

    if(n == 2){
        if(asum == bsum){
            cout << abs(a[0] - b[0]) << endl;
        }
        else{
            cout << -1 << endl;
        }
        return 0;
    }

    if(!(asum >= bsum && (asum - bsum) % (n - 2) == 0)){
        cout << -1 << endl;
        return 0;
    }

    ll op = (asum - bsum) / (n - 2);

    vector<ll> p(n);
    bool valid = true;
    for(int i=0; i<n; i++){
        p[i] = b[i] - (a[i] - op);
        if(p[i] < 0 || p[i] % 2 == 1) valid = false;
    }

    ll psum = accumulate(all(p), 0LL);

    if(psum == op * 2 && valid){
        cout << op << endl;
    }
    else{
        cout << -1 << endl;
    }

    return 0;
}