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
#include <bits/stdc++.h>
#define maxn 50005
using namespace std;

int n;
int wej[maxn];

inline int solve(int t)
{
	int ret = 0;
	for(int i = 2; i <= n; ++i)
	{
		if(t)
		{
			if(wej[i-1] < wej[i]) t=1-t;
			else ++ret, ++i;
		}
		else
		{
			if(wej[i-1] > wej[i]) t=1-t;
			else ++ret, ++i;
		}
	}
	return ret;
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n;
	for(int i = 1; i <= n; ++i) cin >> wej[i];
	int wyn = min(solve(0), solve(1));
	cout << wyn;
		
	return 0;
}