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

int n;
int tab[50001];

int check(bool inc) {
    int prev = tab[0];
    int ret = 0;
    for(int i=1;i<n;i++) {
        int cur = tab[i];
        if(inc) {
            if(cur <= prev) {
                cur = 1000000001;
                ret++;
            }
        } else {
            if(cur >= prev) {
                cur = -1000000001;
                ret++;
            }
        }
        prev = cur;
        inc = !inc;
    }
    return ret;
}

int main() {
    cin >> n;
    for(int i=0;i<n;i++) {
        cin >> tab[i];
    }
    cout << min(check(true), check(false));
    return 0;
}