#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    ll N; cin >> N;
    vector<ll> A(N), B(N);
    rep(i,N) cin >> A[i];
    rep(i,N) cin >> B[i];

    if(N == 2) {
        if(A[0] - B[0] == -(A[1] - B[1])) {
            cout << abs(A[0] - B[0]) << endl;
        } else {
            cout << -1 << endl;
        }
        return 0;
    }

    // N-2ずつ減る
    ll sumA = accumulate(A.begin(), A.end(), 0LL);
    ll sumB = accumulate(B.begin(), B.end(), 0LL);
    if((sumB - sumA) % (N - 2) != 0) { cout << -1 << endl; return 0; }

    ll K = (sumA - sumB) / (N - 2);
    ll cnt = 0;
    rep(i,N) {
        // x + y = K
        // x - y = B - A

        // 2x = K + B - A
        // 2y = K - B + A
        if((K + B[i] - A[i]) % 2 != 0){ cout << -1 << endl; return 0; }
        cnt += (K + B[i] - A[i]) / 2;
    }

    if(cnt == K) {
        cout << cnt << endl;
    } else {
        cout << -1 << endl;
    }
}