1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
//Solution by Mikołaj Kołek

#include "bits/stdc++.h"
#define intin *istream_iterator<int>(cin)

using namespace std;

template<typename Value, typename Modifier>
class SegmentTree {
private:
	struct Node {
		Value val;
		Modifier mod;
		
		Node(Value init) {
			this->val = init;
		}
		
		operator Value() const {
			return mod(val);
		}
	};

	vector<Node> T;
	size_t L = 1;
	
	void update(
		size_t v, 
		size_t vBegin, 
		size_t vEnd, 
		size_t updateBegin, 
		size_t updateEnd, 
		Modifier mod
	) {
		if(vBegin >= updateEnd or vEnd <= updateBegin)
			return;
		if(vBegin >= updateBegin and vEnd <= updateEnd) {
			T[v].mod = mod * T[v].mod; 
			return;
		}
		
		T[2 * v].mod = T[v].mod * T[2 * v].mod;
		T[(2 * v) + 1].mod = T[v].mod * T[(2 * v) + 1].mod;
		T[v].mod = {};
		
		update(2 * v, vBegin, (vBegin + vEnd) / 2, updateBegin, updateEnd, mod);
		update((2 * v) + 1, (vBegin + vEnd) / 2, vEnd, updateBegin, updateEnd, mod);
		
		T[v].val = ((Value) T[2 * v]) + ((Value) T[(2 * v) + 1]);
	}
public:
    SegmentTree(const vector<Value> &values) {
		while(L <= (values.size() + 1))
			L *= 2;
		
		T = vector<Node>(2 * L, ((Value) {}));
		
		for(size_t i = 0; i < values.size(); i++) 
			T[i + L].val = values[i];
		for(size_t i = L - 1; i >= 1; i--)
			T[i].val = ((Value) T[2 * i]) + ((Value) T[(2 * i) + 1]);
	}

    SegmentTree(size_t n, Value value = {}) : SegmentTree(vector<Value>(n, value)) {}
	
    Value query(size_t begin, size_t end) const {
		if(begin >= end)
			return {};
		begin += L; end += L;
		
		bool rEnabled = false;
		Value resL = T[begin], resR = {};
		while(begin / 2 != end / 2) {
			if(begin % 2 == 0)
				resL = resL + T[begin + 1];
			if(end % 2 == 1) {
				resR = T[end - 1] + resR;
				rEnabled = true;
			}
			
			begin /= 2; end /= 2;
			resL = T[begin].mod(resL);
			if(rEnabled)
				resR = T[end].mod(resR);
		}
		
		Value result = resL + resR;
		while(begin /= 2)
			result = T[begin].mod(result);
		
		return result;
	}
	
    void update(size_t begin, size_t end, Modifier modifier) {
		if(begin >= end)
			return;
		
		update(1, 0, L, begin, end, modifier);
	}
};

struct Value {
	int v = 0;
	
    friend Value operator+(Value l, Value r) {
		return { .v = l.v + r.v };
    }
};

struct Modifier {
	int add = 0;
		
    friend Modifier operator*(Modifier l, Modifier r) {		
        return { .add = l.add + r.add };
    }

    Value operator()(Value v) const {		
		return { .v = v.v + add };
    }
};

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	int n = intin;
	vector<int> a(n);
	copy_n(istream_iterator<int>(cin), n, a.begin());
	
	vector<int> sufRes(n + 1), sufMax(n + 1); sufRes[n] = 0;
	deque<pair<int, int>> inc = { { 1e9, 0 } };
	for(int i = n - 1; i >= 0; i--) {
		while(inc.front().first <= a[i])
			inc.pop_front();
		
		sufRes[i] = inc.front().second + 1;
		inc.push_front({ a[i], sufRes[i] });
		sufMax[i] = max(sufMax[i + 1], a[i]);
	}
	
	int maxPref = 0;
	vector<int> prefRes(n + 1);
	SegmentTree<Value, Modifier> tree(1e6 + 2);
	for(int i = 1; i <= n; i++) {
		if(a[i - 1] > maxPref)
			tree.update(0, a[i - 1], { .add = 1 });
		
		prefRes[i] = tree.query(sufMax[i], sufMax[i] + 1).v;
		maxPref = max(maxPref, a[i - 1]);
	}
	
	int res = 0;
	for(int i = 0; i <= n; i++)
		res = max(res, sufRes[i] + prefRes[i]);
	cout << res;
	
	return 0;
}