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#include<bits/stdc++.h>

using namespace std;
const int maxn=50009;
int rosnie[maxn], maleje[maxn];
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n, a;
    cin >> n;
    for(int i=1; i<=n; i++) {
        cin >> a;
        rosnie[i]=a;
        maleje[i]=a;
    }
    int wr=0, wm=0;
    for(int i=2; i<=n; i++) {
        if(i%2==1) {
            if(rosnie[i]<=rosnie[i-1]) {
                wr++;
                rosnie[i]=1000000000;
            }
            if(maleje[i]>=maleje[i-1]) {
                wm++;
                maleje[i]=-1000000000;
            }
        }
        else {
            if(rosnie[i]>=rosnie[i-1]) {
                wr++;
                rosnie[i]=-1000000000;
            }
            if(maleje[i]<=maleje[i-1]) {
                wm++;
                maleje[i]=1000000000;
            }
        }
    }
    int wyn=min(wm, wr);
    cout << wyn;
}