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

int t[50009];
int t2[50009];

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int n;
    cin>>n;
    int wyn1 = 0, wyn2 = 0;
    for(int i = 1; i <= n; i++){
        cin>>t[i];
        t2[i] = t[i];
    }
    for(int i = 2; i <= n; i++){
        if(i % 2 == 0){
            if(t[i - 1] <= t[i]){
                t[i] = -1000000;
                wyn1++;
            }
        }
        if(i % 2 == 1){
            if(t[i - 1] >= t[i]){
                t[i] = 1000000;
                wyn1++;
            }
        }
    }

    for(int i = 2; i <= n; i++){
        if(i % 2 == 1){
            if(t2[i - 1] <= t2[i]){
                t2[i] = -1000000;
                wyn2++;
            }
        }
        if(i % 2 == 0){
            if(t2[i - 1] >= t2[i]){
                t2[i] = 1000000;
                wyn2++;
            }
        }
    }

    cout<<min(wyn1, wyn2);
}