#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int, int>;
int main()
{
    int n;
    cin >> n;
    vector<int> A(n);
    vector<int> B(n);
    rep(i, n)
    {
        cin >> A[i];
    }
    rep(i, n)
    {
        cin >> B[i];
    }
    int sum = 0;
    int md = 0;
    rep(i, n)
    {
        int d = A[i] - B[i];
        sum += d;
        if (d < 0)
            d = -d;
        md = max(d, md);
    }
    int op = -1;
    if (n == 2 && sum == 0)
    {
        op = md;
    }
    else if (sum % (n - 2) == 0 && sum >= 0 && sum / (n - 2) >= md)
    {
        op = sum / (n - 2);
    }
    cout << op << endl;
    return 0;
}