#include "bits/stdc++.h" using namespace std; #define int long long #define REP(i, n) for (int i = 0; i < (int)n; ++i) #define RREP(i, n) for (int i = (int)n - 1; i >= 0; --i) #define FOR(i, s, n) for (int i = s; i < (int)n; ++i) #define RFOR(i, s, n) for (int i = (int)n - 1; i >= s; --i) #define ALL(a) a.begin(), a.end() #define IN(a, x, b) (a <= x && x < b) templateistream&operator >>(istream&is,vector&vec){for(T&x:vec)is>>x;return is;} templateinline void out(T t){cout << t << "\n";} templateinline void out(T t,Ts... ts){cout << t << " ";out(ts...);} templateinline bool CHMIN(T&a,T b){if(a > b){a = b;return true;}return false;} templateinline bool CHMAX(T&a,T b){if(a < b){a = b;return true;}return false;} constexpr int INF = 1e18; template struct SegmentTree{ using F = function; int n; F f; T ti; vector dat; SegmentTree(){} SegmentTree(F f,T ti):f(f),ti(ti){} void init(int n_){ n=1; while(n &v){ int n_=v.size(); init(n_); for(int i=0;i>=1) dat[k]=f(dat[(k<<1)|0],dat[(k<<1)|1]); } T query(int a,int b){ if(a>=b) return ti; T vl=ti,vr=ti; for(int l=a+n,r=b+n;l>=1,r>>=1) { if(l&1) vl=f(vl,dat[l++]); if(r&1) vr=f(dat[--r],vr); } return f(vl,vr); } template int find(int st,C &check,T &acc,int k,int l,int r){ if(l+1==r){ acc=f(acc,dat[k]); return check(acc)?k-n:-1; } int m=(l+r)>>1; if(m<=st) return find(st,check,acc,(k<<1)|1,m,r); if(st<=l&&!check(f(acc,dat[k]))){ acc=f(acc,dat[k]); return -1; } int vl=find(st,check,acc,(k<<1)|0,l,m); if(~vl) return vl; return find(st,check,acc,(k<<1)|1,m,r); } template int find(int st,C &check){ T acc=ti; return find(st,check,acc,1,0,n); } //アウトの条件を渡す }; template< typename T > struct Compress { vector< T > xs; Compress() = default; Compress(const vector< T > &vs) { add(vs); } Compress(const initializer_list< vector< T > > &vs) { for(auto &p : vs) add(p); } void add(const vector< T > &vs) { copy(begin(vs), end(vs), back_inserter(xs)); } void add(const T &x) { xs.emplace_back(x); } void build() { sort(begin(xs), end(xs)); xs.erase(unique(begin(xs), end(xs)), end(xs)); } vector< int > get(const vector< T > &vs) const { vector< int > ret; transform(begin(vs), end(vs), back_inserter(ret), [&](const T &x) { return lower_bound(begin(xs), end(xs), x) - begin(xs); }); return ret; } int get(const T &x) const { return lower_bound(begin(xs), end(xs), x) - begin(xs); } const T &operator[](int k) const { return xs[k]; } }; signed main(){ int N; cin >> N; vectora(N); cin >> a; Compress c(a); c.build(); vectorb(N); REP(i, N) b[i] = c.get(a[i]); int ans = 0; auto f = [&](vector&a) -> int { vectorl(N), r(N); SegmentTreeseg([](int a, int b) {return max(a, b);}, 0ll); seg.build(vector(N)); REP(i, N) { int t = seg.query(0, a[i]); if(seg.query(a[i], a[i] + 1) < t + 1) { seg.set_val(a[i], t + 1); } l[i] = seg.query(a[i], a[i] + 1); } REP(i, N) seg.set_val(i, 0); reverse(ALL(a)); REP(i, N) { int t = seg.query(0, a[i]); if(seg.query(a[i], a[i] + 1) < t + 1) { seg.set_val(a[i], t + 1); } r[i] = seg.query(a[i], a[i] + 1); } int ma = 0; REP(i, N) CHMAX(ma, min(l[i], r[N - i - 1])); reverse(ALL(a)); return ma - 1; }; REP(i, 2) { CHMAX(ans, f(b)); REP(j, N) a[j] *= -1; Compress d(a); d.build(); REP(j, N) b[j] = d.get(a[j]); } out(ans); }