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#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int a[50000];

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    int n;
    cin>>n;
    for(int i=0; i<n; i++)
        cin>>a[i];
    int r1=0,r2=0;
    int c=0;
    while(c<n-1)
    {
        // cout<<c<<" "<<a[c]<<" "<<a[c+1]<<"\n";
        if(c%2==0&&a[c]>=a[c+1])
        {
            // cout<<"wrong "<<c<<"\n";
            r1++;
            c+=2;
        }
        else if(c%2==1&&a[c]<=a[c+1])
        {
            // cout<<"wrong "<<c<<"\n";
            r1++;
            c+=2;
        }
        else
            c++;
    }
    // cout<<"\n";
    c=0;
    while(c<n-1)
    {
        // cout<<c<<" "<<a[c]<<" "<<a[c+1]<<"\n";
        if(c%2==0&&a[c]<=a[c+1])
        {
            // cout<<"wrong "<<c<<"\n";
            r2++;
            c+=2;
        }
        else if(c%2==1&&a[c]>=a[c+1])
        {
            // cout<<"wrong "<<c<<"\n";
            r2++;
            c+=2;
        }
        else
            c++;
    }
    cout<<min(r1,r2);
}