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#include <bits/stdc++.h>
using namespace std;
#define mk make_pair
#define fst first
#define sz(x) x.size()
#define snd second
#define pb push_back
#define VAR(v) #v << " = " << v << " "
#define debug if (0)
#define M_PI 3.14159265358979323846
typedef complex<long double> C;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<ll> Matrix;
const int maxn = (int)1e6 + 9;
const int INF = (int)1e9 + 7;
int mod = (int)1e9 + 7;
int n;
int arr[maxn];

// flag == 1 -> starting with higher

int solve(bool flag)
{
    int cnt = 0;
    int prv = arr[0];
    for (int i = 1; i < n; i++)
    {
        bool cond = (i % 2 == 0) ^ flag;
        // cout << cond << endl;
        if (cond) // next one should be higher
        {
            if (arr[i] <= prv)
                cnt++, prv = 1000001;
            else
                prv = arr[i];
        }
        else
        {
            if (arr[i] >= prv)
                cnt++, prv = -1000001;
            else
                prv = arr[i];
        }
    }
    // cout << flag << " " << cnt << endl;
    return cnt;
}

int main(int argc, char *argv[])
{
    ios::sync_with_stdio(false);
    debug;
    else cin.tie(NULL), cout.tie(NULL);
    cin >> n;
    for (int i = 0; i < n; i++)
        cin >> arr[i];
    cout << min(solve(1), solve(0)) << "\n";
    return 0;
}

/*
1e6
1e6+1
1e6
*/