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
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

int n;
vector<int> v;

int main(){
	ios_base::sync_with_stdio(false);
	cin>>n;
	int res1 = 0, res2=0;
	for(int i=0; i<n; i++){
		int tmp;
		cin>>tmp;
		v.push_back(tmp);
	}
	int prev = v[0];
	for(int i=1; i<n; i++){
		if(i%2==0 && prev <= v[i]){
			res1++;
			prev = -1e9;
			continue;
		}
		if(i%2==1 && prev >= v[i]){
			res1++;
			prev = 1e9;
			continue;
		}
		prev = v[i];
	}
	prev = v[0];
	for(int i=1; i<n; i++){
		if(i%2==1 && prev <= v[i]){
			res2++;
			prev = -1e9;
			continue;
		}
		if(i%2==0 && prev >= v[i]){
			res2++;
			prev = 1e9;
			continue;
		}
		prev = v[i];
	}
	cout<<min(res1, res2)<<"\n";
	return 0;
}