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

typedef long long LL;

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    // -----------------------------------------------------------------------------------
    
    int n;
    cin>>n;
    vector<int> tab(n);
    for(int i=0;i<n;i++)cin>>tab[i];
    int wynik=1e9;
    vector<int> dp = tab;
    int res=0;
    for(int i=1;i<n;i+=2){
        if(dp[i-1]>=dp[i]){
            res++;
            dp[i]=1e9;
        }
        if(i+1>n-1)break;
        if(dp[i]<=dp[i+1]){
            res++;
            dp[i+1]=-1e9;
        }
    }
    wynik=min(wynik,res);

    dp = tab;
    res=0;
    for(int i=1;i<n;i+=2){
        if(dp[i-1]<=dp[i]){
            res++;
            dp[i]=-1e9;
        }
        if(i+1>n-1)break;
        if(dp[i]>=dp[i+1]){
            res++;
            dp[i+1]=1e9;
        }
    }
    wynik=min(wynik,res);

    dp = tab;
    res=1;
    dp[0]=1e9;
    for(int i=1;i<n;i+=2){
        if(dp[i-1]<=dp[i]){
            res++;
            dp[i]=-1e9;
        }
        if(i+1>n-1)break;
        if(dp[i]>=dp[i+1]){
            res++;
            dp[i+1]=1e9;
        }
    }
    wynik=min(wynik,res);

    dp = tab;
    res=1;
    dp[0]=-1e9;
    for(int i=1;i<n;i+=2){
        if(dp[i-1]>=dp[i]){
            res++;
            dp[i]=1e9;
        }
        if(i+1>n-1)break;
        if(dp[i]<=dp[i+1]){
            res++;
            dp[i+1]=-1e9;
        }
    }
    wynik=min(wynik,res);

    cout<<wynik<<endl;

    // -----------------------------------------------------------------------------------

    return 0;
}