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
#include<bits/stdc++.h>
 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("trapv")
 
#define st first
#define nd second
#define pb push_back
#define pp pop_back
#define eb emplace_back
#define mp(a, b) make_pair(a, b)
#define all(x) (x).begin(), (x).end()
#define rev(x) reverse(all(x))
#define sor(x) sort(all(x))
#define sz(x) (int)(x).size()
#define rsz(x) resize(x)
 
using namespace std;
 
///~~~~~~~~~~~~~~~~~~~~~~~~~~
 
template <typename H, typename T> 
ostream& operator<<(ostream& os, pair<H, T> m){
	return os <<"("<< m.st<<", "<<m.nd<<")";
}
template <typename H> 
ostream& operator<<(ostream& os, vector<H> V){
	os<<"{";
	for(int i=0; i<V.size(); i++){
		if(i)os<<" ";
		os<<V[i];
	}
	os<<"}";
	return os;
}
 
void debug(){cerr<<"\n";}
template <typename H, typename... T>
void debug(H h, T... t) {cerr<<h; if (sizeof...(t)) cerr << ", "; debug(t...);}
#define deb(x...) cerr<<#x<<" = ";debug(x);
 
///~~~~~~~~~~~~~~~~~~~~~~~~~
 
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii > vii;
typedef vector<ll> vl;
typedef vector<pll> vll;
typedef string str;
 
#define BOOST ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
 
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
 
const int N=2e5+5, INF=1e9+5, mod=1e9+7;
int dp[2][N];
int solve(vi V){
	int n=V.size();
	for(int i=1; i<n; i++){
		dp[1][i]=1+min(dp[0][i-1], dp[1][i-1]);
		dp[0][i]=dp[1][i-1];
		if(i&1){
			if(V[i]>V[i-1])dp[0][i]=min(dp[0][i], dp[0][i-1]);
		}
		else{
			if(V[i]<V[i-1])dp[0][i]=min(dp[0][i], dp[0][i-1]);
		}
	}
	return min(dp[0][n-1], dp[1][n-1]);
}
int main(){
	//BOOST;
	int n;
	cin>>n;
	vi V(n);
	for(int &i:V)cin>>i;
	dp[1][0]=1;
		int ans=solve(V);
	for(int &i:V)i=-i;
		ans=min(ans, solve(V));
	dp[1][0]=1;
	cout<<ans;
}