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// Arti1990, II UWr

#include <bits/stdc++.h>

#define forr(i, n)                  for(int i=0; i<n; i++)
#define FOREACH(iter, coll)         for(auto iter = coll.begin(); iter != coll.end(); ++iter)
#define FOREACHR(iter, coll)        for(auto iter = coll.rbegin(); iter != coll.rend(); ++iter)
#define lbound(P,K,FUN)             ({auto SSS=P, PPP = P-1, KKK=(K)+1; while(PPP+1!=KKK) {SSS = (PPP+(KKK-PPP)/2); if(FUN(SSS)) KKK = SSS; else PPP = SSS;} PPP;})
#define testy()                     int _tests; scanf("%d", &_tests); FOR(_test, 1, _tests)
#define CLEAR(tab)                  memset(tab, 0, sizeof(tab))
#define CONTAIN(el, coll)           (coll.find(el) != coll.end())
#define FOR(i, a, b)                for(int i=a; i<=b; i++)
#define FORD(i, a, b)               for(int i=a; i>=b; i--)
#define MP                          make_pair
#define PB                          push_back
#define ff                          first
#define ss                          second
#define deb(X)                      X;

#define M 1000000007
#define INF 1000000007LL

using namespace std;

int n, m, a;
int tab[1000007];

int solve()
{
    cin >> n;
    forr(i, n)
        cin >> tab[i];

    int res = n+1, r = 0;
    forr(i, n-1)
        if(!((i%2 == 0 && tab[i] < tab[i+1]) || (i%2 == 1 && tab[i] > tab[i+1])))
        {
            r++;
            i++;
        }
    res = min(res, r);

    r = 0;
    forr(i, n-1)
        if(!((i%2 == 0 && tab[i] > tab[i+1]) || (i%2 == 1 && tab[i] < tab[i+1])))
        {
            r++;
            i++;
        }
    res = min(res, r);

    cout << res << endl;

    return 0;
}

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

    solve();

    return 0;
}