#include <bits/stdc++.h>
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()
#define fi first
#define se second
typedef long long ll;
typedef vector<ll> vec;
typedef vector<vec> mat;

ll N,M,H,W,Q,K,A,B;
string S;
//const ll MOD = 998244353;
const ll MOD = (1e+9) + 7;
typedef pair<ll, ll> P;
const ll INF = (1LL<<58);

int main() {
    cin>>N;
    vec a(N), b(N);
    rep(i,N) cin>>a[i];
    rep(i,N) cin>>b[i];
    ll dif = accumulate(ALL(a), 0LL) - accumulate(ALL(b), 0LL);
    if(N == 2){
        cout<<(dif ? -1 : abs(a[0] - b[0]))<<endl;
    }else if(dif % (N - 2) != 0){
        cout<<-1<<endl;
    }else{
        ll num = dif / (N - 2), temp = 0;
        rep(i,N){
            ll ch = b[i] + num - a[i];
            if(ch < 0 || (ch&1)){
                cout<<-1<<endl;
                return 0;
            }else{
                temp += ch / 2;
            }
        }
        cout<<(num == temp ? num : -1)<<endl;
    }
}