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#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

template<typename T>
int sgn(T val) {
    return (T(0) < val) - (val < T(0));
}

const int MAX = 1000001;

int calc(vector<int> &elements, int direction) {
    int changes = 0;
    int index = 0;
    while (elements.size() - index >= 2) {
        int a = elements[index];
        int b = elements[index + 1];

        if (direction != sgn(b - a)) {
            elements[index + 1] = a + direction * MAX;
            changes++;
        }

        direction = -direction;
        index++;
    }

    return changes;
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int n;
    cin >> n;
    vector<int> elementsA(n);
    vector<int> elementsB(n);

    for (auto i = 0; i < n; i++) {
        int v;
        cin >> v;
        elementsA[i] = v;
        elementsB[i] = v;
    }

    int resultA = calc(elementsA, 1);
    int resultB = calc(elementsB, -1);

    cout << min(resultA, resultB) << endl;

    return 0;
}