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#include <bits/stdc++.h>
using namespace std;
using ll = long long;

#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) ;
#endif

#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)

#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repp(i, n, m) for (int i = (n); i < (m); ++i)

#define repr(i, n) for (int i = (n) - 1; i >= 0; --i)
#define reppr(i, n, m) for (int i = (m) - 1; i >= (n); --i)

using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using pi = pair<int, int>;
using pll = pair<ll, ll>;

template <typename T, typename V> void mini(T& a, V b) {if (b < a) a = b; }
template <typename T, typename V> void maxi(T& a, V b) {if (b > a) a = b; }

int sol(const deque<int> &d) { // d[0] > d[1] < d[2] > d[3]
    int n = d.size();

    vi nonch(n, n), ch(n, n);

    nonch[0] = 0;
    ch[0] = 1;

    for (int i = 1; i < n; ++i) {
        mini(ch[i], nonch[i-1] + 1);
        mini(ch[i], ch[i-1] + 1);

        mini(nonch[i], ch[i-1]);

        if ((d[i] > d[i-1] && i%2 == 0) || (d[i] < d[i-1] && i%2 == 1))
            mini(nonch[i], nonch[i-1]);
    }

    debug(d, n, nonch, ch);
    return min(nonch.back(), ch.back());
}

void solve() {
    int n;
    cin >> n;
    deque<int> d(n);
    for (auto &a : d) cin >> a;

    int s1 = sol(d);
    d.push_front(1e9);
    int s2 = sol(d);

    debug(s1, s2);

    cout << min(s1, s2) << '\n';
}

int main() {
#ifndef DEBUG
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#endif
    int z = 1;
    // scanf("%d", &z);
    while (z--)
        solve();
    return 0;
}