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
#include <bits/stdc++.h>
#define int long long
#define cln cout<<"\n---------------\n"
using namespace std;

constexpr int N = 5e4+7;
constexpr int MOD = 1e9+7;

int licz (vector <int> T, bool k) {
    int r = 0, n = T.size();
    for (int i=1; i<n; ++i) {
        if (k) {
            if (T[i] >= T[i-1]) {
                r++;
                T[i] = -1e6+1;
            }
        }
        else {
            if (T[i] <= T[i-1]) {
                r++;
                T[i] = 1e6+1;
            }
        }
        if (k) k = false;
        else k = true;
    }
    return r;
}


int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    int n; cin>>n;
    vector <int> T(n);
    for (int i=0; i<n; ++i) {
        cin>>T[i];
    }
    
    int res = min(licz(T, true), licz(T, false));
    cout<<res;
    
    return 0;
}