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#include <bits/stdc++.h>

using namespace std;

int ceil2(int n) {
    if(n%2==0) return n/2;
    return n/2+1;
}

int main() {
    int n, a, aprev;
    scanf("%d", &n);


    int slope=1; int count1=0; int count2=0; int changes1=0; int changes2=0;
    scanf("%d",&aprev);
    for (int i = 1; i < n; i++) {
        scanf("%d", &a);
//       printf("%d %d\n",aprev,a);
        int ok1=false; int ok2=false;
        if((a-aprev)*slope > 0) ok1=true;

        if((a-aprev)*slope < 0) ok2=true;

        if(!ok1) count1++;
        else {
            changes1+=ceil2(count1);
            count1=0;
        }

        if(!ok2) count2++;
        else {
            changes2+=ceil2(count2);
            count2=0;
        }

        slope = -slope;
        aprev=a;
    }
    changes1+=ceil2(count1);

    changes2+=ceil2(count2);



    int changes=min(changes1,changes2);

//    printf("%d\n",changes1);
//    printf("%d\n",changes2);
    printf("%d\n",changes);
    return 0;
}