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

const int MAXX = 1e9;
const int MINX = -1e9;

int le(vector<int> data) {
    int res = 0, n = data.size();
    for (int i = 1;i < n;i += 2) {
        if (data[i] <= data[i - 1]) {
            ++res;
            data[i] = MAXX;
        }
        else if (i + 1 < n && data[i] <= data[i + 1]) {
            data[i + 1] = MINX;
            ++res;
        }
    }

    return res;
}

int gr(vector<int> data) {
    int res = 0, n = data.size();
    for (int i = 1;i < n;i += 2) {
        if (data[i] >= data[i - 1]) {
            ++res;
            data[i] = MINX;
        }
        else if (i + 1 < n && data[i] >= data[i + 1]) {
            data[i + 1] = MAXX;
            ++res;
        }
    }

    return res;
}

void solve() {
    int n;
    cin >> n;

    vector<int> data(n);
    for (int& d : data) cin >> d;



    cout << min(le(data), gr(data)) << "\n";
}

int32_t main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
}