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#include <cstdio>
#include <vector>
using std::vector;
using std::min;


int res(vector<int> &a, bool up) {
    int r=0;
    for(int i=1;i<a.size();i++) {
        if(up) {
            if(a[i-1]>=a[i]) {
                r++;
                i++;
            }
        }
        else {
            if(a[i-1]<=a[i]) {
                r++;
                i++;
            }
        }
        up = !up;
    }
    return r;
}


int main() {
    int n;
    scanf("%d", &n);
    vector<int> a;
    for(int i=0;i<n;i++) {
        int a_i;
        scanf("%d", &a_i);
        a.push_back(a_i);
    }
    printf("%d\n", min(res(a, true), res(a, false)));

    return 0;
}