//#define _GLIBCXX_DEBUG #include #define rep(i, n) for(int i=0; i; using vs = vector; using vi = vector; using vvi = vector; template using PQ = priority_queue; template using PQG = priority_queue, greater >; const int INF = 100010001; const ll LINF = (ll)INF*INF*10; template inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);} template inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);} template istream &operator>>(istream &is, pair &p) { return is >> p.first >> p.second;} template ostream &operator<<(ostream &os, const pair &p) { return os << p.first << ' ' << p.second;} const int N = 150000; //head int n; int a[N]; vi box(22*N+1); P J; int main() { ios::sync_with_stdio(false); cin.tie(0); cin >> n; rep(i, n) cin >> a[i]; rep(i, 1<>j&1) { d += a[j]; } } if(box[d]) { J = P(box[d], i); break; } box[d] = i; if(i == (1<>i&1) h++; if(J.second>>i&1) h--; cout << a[i]*h; } cout << endl; }