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#include <algorithm>
#include <limits>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <iostream>

using namespace std;

vector<int> d;

int ile(bool wg)
{
    int wyn=0;
    for (int i=1; i<d.size(); )
    {
        if ((wg && d[i-1]<d[i]) || (!wg && d[i]<d[i-1]))
        {
            wg=!wg;
            ++i;
        }
        else
        {
            ++wyn;
            i+=2;
        }
    }
    return wyn;
}

int main()
{
    ios_base::sync_with_stdio(false);
    int n;
    cin>>n;
    for (int i=0; i<n; ++i)
    {
        int a;
        cin>>a;
        d.push_back(a);
    }
    cout<<min(ile(false), ile(true))<<endl;
    return 0;
}