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#include <bits/stdc++.h>
using namespace std;
constexpr int INF = 1e9;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, curr;
    cin >> n >> curr;
    int prevUp = curr, prevDown = curr;
    int upRes = 0, downRes = 0;
    for (int i = 0; i < n - 1; ++i) {
        cin >> curr;
        if (i % 2) {
            if (prevUp <= curr) {
                ++upRes;
                prevUp = -INF;
            } else {
                prevUp = curr;
            }
            if (prevDown >= curr) {
                ++downRes;
                prevDown = INF;
            } else {
                prevDown = curr;
            }
        } else {
            if (prevUp >= curr) {
                ++upRes;
                prevUp = INF;
            } else {
                prevUp = curr;
            }
            if (prevDown <= curr) {
                ++downRes;
                prevDown = -INF;
            } else {
                prevDown = curr;
            }
        }
    }
    cout << min(upRes, downRes);
}