#include using namespace std; using int128 = __int128_t; using int64 = long long; using int32 = int; using uint128 = __uint128_t; using uint64 = unsigned long long; using uint32 = unsigned int; #define ALL(obj) (obj).begin(),(obj).end() template using priority_queue_reverse = priority_queue,greater>; constexpr int64 MOD = 1'000'000'000LL + 7; //' constexpr int64 MOD2 = 998244353; constexpr int64 HIGHINF = 1'000'000'000'000'000'000LL; constexpr int64 LOWINF = 1'000'000'000'000'000LL; //' constexpr long double PI = 3.1415926535897932384626433L; template vector multivector(size_t N,T init){return vector(N,init);} template auto multivector(size_t N,T... t){return vector(N,multivector(t...));} template void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}} template ostream &operator<<(ostream &o, const map&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;} template ostream &operator<<(ostream &o, const set&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;} template ostream &operator<<(ostream &o, const multiset&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;} template ostream &operator<<(ostream &o, const vector&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;} template ostream &operator<<(ostream &o, const deque&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;} template ostream &operator<<(ostream &o, const pair&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;} void print(void) {cout << endl;} template void print(Head&& head) {cout << head;print();} template void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward(tail)...);} template void chmax(T& a, const T b){a=max(a,b);} template void chmin(T& a, const T b){a=min(a,b);} vector split(const string &str, const char delemiter) {vector res;stringstream ss(str);string buffer; while( getline(ss, buffer, delemiter) ) res.push_back(buffer); return res;} inline constexpr int msb(int x) {return x?31-__builtin_clz(x):-1;} inline constexpr int64 ceil_div(const int64 a,const int64 b) {return (a+(b-1))/b;}// return ceil(a/b) void YN(bool flg) {cout << (flg ? "YES" : "NO") << endl;} void Yn(bool flg) {cout << (flg ? "Yes" : "No") << endl;} void yn(bool flg) {cout << (flg ? "yes" : "no") << endl;} /* * @title SegmentTree - 非再帰抽象化セグメント木 * @docs md/segment/SegmentTree.md */ template class SegmentTree { using TypeNode = typename Operator::TypeNode; size_t length; size_t num; vector node; vector> range; inline void build() { for (int i = length - 1; i >= 0; --i) node[i] = Operator::func_node(node[(i<<1)+0],node[(i<<1)+1]); range.resize(2 * length); for (int i = 0; i < length; ++i) range[i+length] = make_pair(i,i+1); for (int i = length - 1; i >= 0; --i) range[i] = make_pair(range[(i<<1)+0].first,range[(i<<1)+1].second); } public: //unitで初期化 SegmentTree(const size_t num): num(num) { for (length = 1; length <= num; length *= 2); node.resize(2 * length, Operator::unit_node); build(); } //vectorで初期化 SegmentTree(const vector & vec) : num(vec.size()) { for (length = 1; length <= vec.size(); length *= 2); node.resize(2 * length, Operator::unit_node); for (int i = 0; i < vec.size(); ++i) node[i + length] = vec[i]; build(); } //同じinitで初期化 SegmentTree(const size_t num, const TypeNode init) : num(num) { for (length = 1; length <= num; length *= 2); node.resize(2 * length, Operator::unit_node); for (int i = 0; i < length; ++i) node[i+length] = init; build(); } //[idx,idx+1) void update(size_t idx, const TypeNode var) { if(idx < 0 || length <= idx) return; idx += length; node[idx] = Operator::func_merge(node[idx],var); while(idx >>= 1) node[idx] = Operator::func_node(node[(idx<<1)+0],node[(idx<<1)+1]); } //[l,r) TypeNode get(int l, int r) { if (l < 0 || length <= l || r < 0 || length < r) return Operator::unit_node; TypeNode vl = Operator::unit_node, vr = Operator::unit_node; for(l += length, r += length; l < r; l >>=1, r >>=1) { if(l&1) vl = Operator::func_node(vl,node[l++]); if(r&1) vr = Operator::func_node(node[--r],vr); } return Operator::func_node(vl,vr); } //range[l,r) return [l,r] search max right int prefix_binary_search(int l, int r, TypeNode var) { assert(0 <= l && l < length && 0 < r && r <= length); TypeNode ret = Operator::unit_node; size_t off = l; for(size_t idx = l+length; idx < 2*length && off < r; ){ if(range[idx].second<=r && !Operator::func_check(Operator::func_node(ret,node[idx]),var)) { ret = Operator::func_node(ret,node[idx]); off = range[idx++].second; if(!(idx&1)) idx >>= 1; } else{ idx <<=1; } } return off; } //range(l,r] return [l,r] search max left int suffix_binary_search(const int l, const int r, const TypeNode var) { assert(-1 <= l && l < (int)length-1 && 0 <= r && r < length); TypeNode ret = Operator::unit_node; int off = r; for(size_t idx = r+length; idx < 2*length && l < off; ){ if(l < range[idx].first && !Operator::func_check(Operator::func_node(node[idx],ret),var)) { ret = Operator::func_node(node[idx],ret); off = range[idx--].first-1; if(idx&1) idx >>= 1; } else{ idx = (idx<<1)+1; } } return off; } void print(){ // cout << "node" << endl; // for(int i = 1,j = 1; i < 2*length; ++i) { // cout << node[i] << " "; // if(i==((1< struct NodeMaxPointUpdate { using TypeNode = T; inline static constexpr TypeNode unit_node = 0; inline static constexpr TypeNode func_node(TypeNode l,TypeNode r){return max(l,r);} inline static constexpr TypeNode func_merge(TypeNode l,TypeNode r){return r;} inline static constexpr bool func_check(TypeNode nodeVal,TypeNode var){return var > nodeVal;} }; //一点更新 区間最小 template struct NodeSumPointUpdate { using TypeNode = T; inline static constexpr TypeNode unit_node = 0; inline static constexpr TypeNode func_node(TypeNode l,TypeNode r){return l+r;} inline static constexpr TypeNode func_merge(TypeNode l,TypeNode r){return r;} inline static constexpr bool func_check(TypeNode nodeVal,TypeNode var){return var > nodeVal;} }; /** * @url * @est */ int main() { cin.tie(0);ios::sync_with_stdio(false); int N; cin >> N; vector A(N),B,C(N,0); for(int i=0;i> A[i]; for(int i=0;i+1A[i+1]); B = A; sort(ALL(B)); corner(A==B,0); SegmentTree> ma(A); SegmentTree> su(C); for(int i = N-1; 1 <= i; --i) { if(B[i]!=A[i]) break; if(ma.get(0,i)>A[i]) continue; if(su.get(0,i-1)!=1) continue; if(A[0]