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#include <iostream>
#define boost ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
using namespace std;

int main() {
    boost;
    int l;
    cin >> l;

    int a = 0, b = 0;
    bool ac = false, bc = false;

    int p, c;

    cin >> c;
    for (int i = 1; i < l; ++i) {
        p = c;
        cin >> c;
        if (i % 2 == 0) {
            if (c > p || ac) {
                ac = false;
            } else {
                a++;
                ac = true;
            }

            if (c < p || bc) {
                bc = false;
            } else {
                b++;
                bc = true;
            }
        } else {
            if (c < p || ac) {
                ac = false;
            } else {
                a++;
                ac = true;
            }

            if (c > p || bc) {
                bc = false;
            } else {
                b++;
                bc = true;
            }
        }
    }
    cout << ((a < b)? a : b) << "\n";
    return 0;
}