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#include <bits/stdc++.h>
using namespace std;
const int PIN = 1e9;
const int MIN = -1e9;
int n, L1=0, L2=0, L3=0, L4=0, wmw[50500], mwm[50500];
string s;

int main () {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n;
    for (int i=1; i<=n; i++) {
        cin >> wmw[i];
        mwm[i]=wmw[i];
    }

    for (int i=2; i<=n; i++) {
        if (i%2==0) {
            if(wmw[i-1]<=wmw[i]) {
                wmw[i]=MIN;
                L1++;
            }
            if (mwm[i-1]>=mwm[i]) {
                mwm[i]=PIN;
                L2++;
            }
        }
        if (i%2==1) {
            if(wmw[i-1]>=wmw[i]) {
                wmw[i]=PIN;
                L1++;
            }
            if (mwm[i-1]<=mwm[i]) {
                mwm[i]=MIN;
                L2++;
            }
        }
    }

    // for (int i=1; i<=n; i++) {
    //     cout << mwm[i] << " " << wmw[i] << '\n';
    // }
    cout << min(L1, L2);
    return 0;
}