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#include <iostream>
#include <map>
#include <unordered_map>
#include <vector>
#include <unordered_set>
#include <set>
#include <queue>
#include <utility>
#include <algorithm>
#include <cassert>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> pi;
typedef vector<ll> vi;


const int S = 1e6 + 7;
const int mod = 1e9 + 7;
ll tab[S], n, m, dp[S][3];

// inject here

void solve(){
    string s;
    cin >> n;
    
    ll res = mod;
    for (int o = 0; o < 2; o ++){
        // max      min        no change
        dp[0][0] = dp[0][1] = dp[0][2] = 0;
        for (int i = 1; i <= n; i ++){
            cin >> tab[i];
            bool is_max = i & 1 ^ o;

            dp[i][0] = min(dp[i - 1][1], dp[i - 1][2]) + 1;
            dp[i][1] = min(dp[i - 1][0], dp[i - 1][2]) + 1;

            if (is_max) dp[i][1] = mod;
            else        dp[i][0] = mod;

        
            dp[i][2] = dp[i - 1][is_max];
            bool are_in_order = (
                !is_max ? 
                    tab[i - 1] < tab[i] :
                    tab[i] < tab[i - 1]
            );
            if (!i || are_in_order)
                dp[i][2] = min(dp[i][2], dp[i - 1][2]);

            //cout << "o = " << o << " i = " << i << " [" << dp[i][0] << ", " << dp[i][1] << ", " << dp[i][2] << "]\n";
        }
        for (int i = 0; i < 3; i ++){
            res = min(res, dp[n][i]);
        }
    }
    cout << res << "\n";
        
}


int main(){
    ios_base::sync_with_stdio(0);
    int t = 1;
   // cin >> t;
    while (t --)
        solve();

    return 0;
}