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//#pragma GCC optimize("Ofast")
//#pragma GCC target ("avx2")
//#pragma GCC optimization ("O3")
//#pragma GCC optimization ("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
using namespace std;
//typedef tree<pair<int,int>,null_type,less<pair<int,int>>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
#define ll long long
#define ull unsigned long long int
#define pb push_back
#define mp make_pair
#define vi vector<int>
#define pii pair<int,int>
#define pss pair<short,short>
#define pld pair<long double,long double >
#define ld long double
#define piii  pair<pii,int>
#define vii vector<pair<int,int> >
#define st first
#define nd second
#define pll pair<ll,ll>
#define speed ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define M_PI 3.14159265358979323846
//#define int long long
const int mod=1000000007;
//const int mod=1009;
//const int mod=998244353;
const int inf=1000000009;
const long long INF=1000000000000000009;
const long long big=1000000000000000;
const long double eps=0.000000000000000000001;
int T[100005],P[100005];
int wynik=inf;
int n;
void funkcja(int maska){
    P[1]=T[1];
    int cur=0;
    for(int i=2;i<=n;i++){
        P[i]=T[i];
        int r=(maska+i)%2;
        if(r==0&&P[i]<=P[i-1]){
            cur++;
            P[i]=inf;
        }
        if(r==1&&P[i]>=P[i-1]){
            cur++;
            P[i]=-inf;
        }
    }
    wynik=min(wynik,cur);
}
void solve()
{
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>T[i];
    funkcja(0);
    funkcja(1);
    cout<<wynik;
}
    
int32_t main(){
    speed
    int t = 1;
    //cin >> t;
    while(t--){
        solve();
    }
    return 0;
}