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#include <bits/stdc++.h>

#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define st first
#define nd second

using namespace std;
 
#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename \
	enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
	ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
	*this << "[";
	for (auto it = d.b; it != d.e; ++it)
	*this << ", " + 2 * (it == d.b) << *it;
	ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
 
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi = vector<int>;
using vll = vector<ll>;

const int kInf = 1000 * 1000 * 1000;

int Sign(int x) {
	if (x > 0) return 1;
	if (x == 0) return 0;
	return -1;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout << fixed << setprecision(11);
	cerr << fixed << setprecision(6);
	
	
	int n;
	cin >> n;
	
	vi seq(n);
	for (int &x : seq) { cin >> x; }
	int ans = n + 1;
	
	for (int iter = 0; iter < 2; ++iter) {
		vi mod_seq = seq;
		int cand_ans = 0;
		for (int i = 1; i < n; ++i) {
			const int expected_sign = (i % 2 == 1) ? 1 : -1;
			const int got_sign = Sign(mod_seq[i] - mod_seq[i - 1]);
			if (expected_sign != got_sign) {
				mod_seq[i] = expected_sign * kInf;
				++cand_ans;
			}
		}
		
		ans = min(ans, cand_ans);

		for (int &x : seq) { x = -x; }
	}
	
	cout << ans << "\n";
}