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#include <bits/stdc++.h>
using namespace std;

int main(){
    int n; cin>>n;
    vector<int> values(n, 0);
    vector<int> changes(n-1, 0);
    for(int i=0; i<n; i++) cin>>values[i];
    for(int i=0; i<n-1; i++){
        if(values[i+1]>values[i]) changes[i] = 1;
        else if(values[i+1]<values[i]) changes[i] = 0;
        else changes[i] = 2;

    }
    // first case
    int first_result = 0;
    for(int i=0; i<n-1; i++){
        if(i%2==0){
            if(changes[i]!=0){
                first_result++;
                i++;
            }
        } else{
            if(changes[i]!=1){
                first_result++;
                i++;
            }
        }
    }
    // second case
    int second_result = 0;
    for(int i=0; i<n-1; i++){
        if(i%2==0){
            if(changes[i]!=1){
                second_result++;
                i++;
            }
        } else{
            if(changes[i]!=0){
                second_result++;
                i++;
            }
        }
    }
    // output
    cout<<min(first_result, second_result);
    return 0;
}