#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const ld EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

int main(){
    ll N;
    cin >> N;
    ll A[N], B[N];
    rep(i, N) cin >> A[i];
    rep(i, N) cin >> B[i];
    ll sum = 0;
    rep(i, N) sum += A[i]-B[i];
    if(N==2){
        if(sum != 0) cout << -1 << endl;
        else cout << abs(B[0]-A[0]) << endl;
        return 0;
    }
    if(sum < 0 || sum%(N-2) != 0) {cout << -1 << endl; return 0;}
    ll x = sum/(N-2);
    rep(i, N) A[i] -= x;
    bool ans = true;
    rep(i, N){
        ll d = B[i]-A[i];
        if(d < 0 || d%2 != 0) ans = false;
    }
    if(ans) cout << x << endl;
    else cout << -1 << endl;
}