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#include <iostream>
#include <set>
#include <map>
#include <algorithm>

using namespace std;

enum expectation {
    higher, lower
};

expectation neg(expectation expectation) {
    return expectation == lower ? higher : lower;
}

unsigned int cnt(expectation first_expectation, vector<int> nums) {
    unsigned idx = 1;

    expectation curr = neg(first_expectation);
    unsigned cnt = 0;
    while (idx < nums.size()) {
        if (curr == lower && nums[idx] >= nums[idx - 1]) {
            nums[idx] = -10000000;
            cnt += 1;
        }
        if (curr == higher && nums[idx] <= nums[idx - 1]) {
            nums[idx] = 10000000;
            cnt += 1;
        }

        curr = neg(curr);
        idx += 1;
    }

    return cnt;
}

int main() {
    ios_base::sync_with_stdio(false);

    int a, n;
    vector<int> nums;

    cin >> n;
    while (n--) {
        cin >> a;
        nums.push_back(a);
    }

    unsigned first_low = cnt(lower, nums);
    unsigned first_high = cnt(higher, nums);

    cout << min(first_low, first_high) << endl;
    return 0;
}