#include #define rep(i,n) for (int i = 0; i < (n); ++i) #define rrep(i,n) for (int i = (n)-1; i >= 0; i--) #define rep2(i,s,n) for (int i = (s); i < (n); ++i) #define all(a) a.begin(),a.end() #define rall(a) a.rbegin(),a.rend() #define pb push_back #define eb emplace_back #define vi vector #define vvi vector> #define vl vector #define vvl vector> #define vd vector #define vs vector #define vc vector #define vb vector #define vp vector

using namespace std; using ll = long long; using P = pair; using LP = pair; template istream& operator>>(istream &is,pair &p) { return is >> p.first >> p.second; } template ostream& operator<<(ostream &os,const pair &p) { return os<<'{'< istream& operator>>(istream &is,vector &v) { for(T &t:v){is>>t;} return is; } template ostream& operator<<(ostream &os,const vector &v) { os<<'[';rep(i,v.size())os< bool chmin(T& a,T b) {if(a > b){a = b; return true;} return false;} template bool chmax(T& a,T b) {if(a < b){a = b; return true;} return false;} const int inf = 1001001001; const ll linf = 1001001001001001001; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); int n; cin >> n; vi a(n),b(n); cin >> a >> b; ll sa = accumulate(all(a),0LL); ll sb = accumulate(all(b),0LL); ll d = sa-sb; if(d < 0) { cout << -1 << endl; return 0; } if(n == 2) { if(d == 0) cout << 0 << endl; else cout << -1 << endl; return 0; } if(d%(n-2) != 0) { cout << -1 << endl; return 0; } ll l = d/(n-2); ll cnt = 0; rep(i,n) { ll now = b[i]-a[i]+l; if(now&1) { cout << -1 << endl; return 0; } now /= 2; if(now < 0 or now > l) { cout << -1 << endl; return 0; } cnt += now; } cout << (l == cnt ? l : -1) << endl; }