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
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    ll n;
    cin >> n;
    ll aRos[n+1];
    ll aMal[n+1];
    for (ll i = 0; i < n; ++i) {
        ll x;
        cin >> x;
        aRos[i] = x;
        aMal[i] = x;
    }
    aRos[n] = 0; // 121
    aMal[n] = 0; // 212
    ll ansRos = 0;
    ll ansMal = 0;
    bool change = false;
    for (ll i = 0; i < n-1; ++i) {
        if (change) {
            if (aRos[i] <= aRos[i+1]) {
                ansRos++;
                aRos[i+1] = min(aRos[i+2]-1, aRos[i]-1);
            }
            if (aMal[i] >= aMal[i+1]) {
                ansMal++;
                aMal[i+1] = max(aMal[i+2]+1, aMal[i]+1);
            }
            change = false;
        }else {
            if (aRos[i] >= aRos[i+1]) {
                ansRos++;
                aRos[i+1] = max(aRos[i+2]+1, aRos[i]+1);
            }
            if (aMal[i] <= aMal[i+1]) {
                ansMal++;
                aMal[i+1] = min(aMal[i+2]-1, aMal[i]-1);
            }
            change = true;
        }

    }
    cout << min(ansMal, ansRos) << endl;
    return 0;
}