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/******************************************************************************

                              Online C++ Compiler.
               Code, Compile, Run and Debug C++ program online.
Write your code in this editor and press "Run" button to compile and execute it.

*******************************************************************************/

#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll q=1e6+1;
ll n,res,t[q],d[q];
int main()
{
    cin>>n;
    for(ll i=1; i<=n; i++){ //pierwsza jest większa
        cin>>t[i];
        d[i]=t[i];
        if(i!=1){
            if(d[i]>=d[i-1] && i%2==0){
                res++;
                d[i]=-1e6-100;
            }
            if(d[i]<=d[i-1] && i%2==1){
                res++;
                d[i]=1e6+100;
            }
        }
        //cout<<d[i]<<" ";
    }
    //cout<<"\n";
    ll licz=0;
    for(ll i=1; i<=n; i++){ //pierwsza jest mnniejsza
        d[i]=t[i];
        if(i!=1){
            if(d[i]<=d[i-1] && i%2==0){
                licz++;
                d[i]=1e6+100;
            }
            if(d[i]>=d[i-1] && i%2==1){
                licz++;
                d[i]=-1e6-100;
            }
        }
        //cout<<d[i]<<" ";
    }
    cout<<min(res,licz);
    return 0;
}