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#include <iostream>
#include <vector>

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(NULL);
    
    int n;
    std::vector<int> data;
    std::cin >> n;
    for (int i=0; i<n; i++) {
        int val;
        std::cin >> val;
        data.push_back(val);
    }
    
    int lowResult = 0;
    int lowLast = data[0];
    int highResult = 0;
    int highLast = data[0];
    
    for (int i=1; i<n; i++) {
        int val = data.at(i);
        if (i % 2 == 1) {
            if (lowLast >= val) {
                lowResult++;
                lowLast = 10000000;
            } else {
                lowLast = val;
            }
            
            if (highLast <= val) {
                highResult++;
                highLast = -10000000;
            } else {
                highLast = val;
            }
        } else {
            if (highLast >= val) {
                highResult++;
                highLast = 10000000;
            } else {
                highLast = val;
            }
            
            if (lowLast <= val) {
                lowResult++;
                lowLast = -10000000;
            } else {
                lowLast = val;
            }
        }
    }

    std::cout<< std::min(highResult, lowResult) << "\n";
}