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
#include <bits/stdc++.h>

using namespace std;

const int N = 50005;
const int D = 1000005;

int n;
int tab[N];
int kopia[N];
int hop;
int ans;

int main(){

	cin.tie(0);
	ios_base::sync_with_stdio(0);

	cin >> n;

	for(int i = 0; i < n; i++){
		cin >> kopia[i];
		tab[i] = kopia[i];
	}

	ans = n;

	for(int i = 0; i < 2; i++){

		hop = 0;

		for(int i = 1; i < n; i++){
			if(i%2 == 0){
				if(tab[i] >= tab[i-1]){
					tab[i] = -D;
					hop++;
					//cout << i << "\n";
				}
			} else {
				if(tab[i] <= tab[i-1]){
					tab[i] = D;
					hop++;
					//cout << i << "\n";
				}
			}
		}

		for(int i = 0; i < n; i++){
			tab[i] = -kopia[i];
		}
		
		ans = min(ans, hop);
	}

	cout << ans;
}