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#include <iostream>
#include <vector>
#define MAX 1000000000
#define MIN -1000000000

using namespace std;

vector<int> ascending, descending;

int solution(vector<int>&, bool, int);

int main() {
    
    ios_base::sync_with_stdio(false);
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        
        int next;
        cin >> next;
        ascending.push_back(next);
        descending.push_back(next);
    }
    
    int aedits = solution(ascending, true, n);
    int dedits = solution(descending, false, n);
    cout << (aedits < dedits ? aedits : dedits);
    return 0;
}

int solution(vector<int>& store, bool dir, int size) {
    
    int ret = 0;
    for (int i = 1; i < size; i++) {
        
        if (dir ? (store[i - 1] >= store[i]) : store[i - 1] <= store[i]) {
            
            store[i] = dir ? MAX : MIN;
            ret++;
        }
        
        dir = !dir;
    }
    
    return ret;
}