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#include <iostream>
#include <vector>

using namespace std;

int getResult(vector<int> nums, bool direction) {
    int n = nums.size();
    const int mmax = 1e9;
    const int mmin = -1e9;
    int result = 0;
    for(int i = 1; i < n; ++i) {
        if(direction) {
            if(nums[i] >= nums[i - 1]) {
                nums[i] = mmin;
                ++result;
            }
        } else {
            if(nums[i] <= nums[i - 1]) {
                nums[i] = mmax;
                ++result;
            }
        }
        direction = !direction;
    }
    return result;
}

int main() {
    ios_base::sync_with_stdio(0);
    int n;
    cin >> n;
    vector<int> nums(n);
    for(int i = 0; i < n; ++ i) cin >> nums[i];
    int result = min(getResult(nums, true), getResult(nums, false));
    cout << result << "\n";
}