#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif
#include<bits/stdc++.h>
using namespace std;
#define rep(i,s,t) for(ll i = (ll)(s); i < (ll)(t); i++)
#define rrep(i,s,t) for(ll i = (ll)(s-1);(ll)(t) <= i; i--)
#define all(x) (x).begin(), (x).end()
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> Pll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
constexpr ll INF = numeric_limits<ll>::max()/4;
constexpr ll n_max = 2e5+10;
#define int ll

template <typename A, typename B>
string to_string(pair<A, B> p);
string to_string(const string &s) {return '"' + s + '"';}
string to_string(const char *c) {return to_string((string) c);}
string to_string(bool b) {return (b ? "true" : "false");}
template <size_t N>
string to_string(bitset<N> v){
    string res = "";
    for(size_t i = 0; i < N; i++) res += static_cast<char>('0' + v[i]);
    return res;
}
template <typename A>
string to_string(A v) {
    bool first = true;
    string res = "{";
    for(const auto &x : v) {
        if(!first) res += ", ";
        first = false;
        res += to_string(x);
    }
    res += "}";
    return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p){return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";}

void debug_out() {cerr << endl;}
template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << to_string(H);
    debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template<class T>
bool chmax(T &a, T b){if(a < b){a = b; return true;} return false;}
template<class T>
bool chmin(T &a, T b){if(a > b){a = b; return true;} return false;}

signed main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll n; cin >> n;
    vector<ll> a(n);
    for(int i = 0; i < n; i++) cin >> a[i];
    vector<ll> b(n);
    for(int i = 0; i < n; i++) cin >> b[i];
    ll tmp = 0;
    rep(i,0,n){
        tmp += abs(a[i] - b[i]) % 2;
    }
    if(tmp != 0 && tmp != n){
        cout << -1 << "\n";
        return 0;
    }

    auto c = [&](ll x){
        rep(i,0,n)a[i] -= x;
        ll sum = 0;
        bool ok = true;
        rep(i,0,n){
            if(b[i] >= a[i]){
                ok = false;
            }
            if(~(b[i] - a[i]) & 1) ok = false;
            sum += (b[i] - a[i]) / 2;
        }
        ok &= sum == x;
        if(ok){
            cout << sum << "\n";
        }
        else{
            cout << -1 << "\n";
        }
    };


    ll asum = 0, bsum = 0;
    rep(i,0,n){
        asum += a[i];
        bsum += b[i];
    }

    ll t = n - 2;
    if(t == 0){
        if(asum == bsum){
            cout << abs(a[0] - b[0]) << "\n";
        }
        else{
            cout << -1 << "\n";
        }
        return 0;
    }
    if((asum - bsum) < 0 || (asum - bsum) % t != 0){
        cout << -1 << "\n";
    }
    else{
        ll x = (asum - bsum) / t;
        c(x);
    }
}