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#include <bits/stdc++.h>
using namespace std;
typedef vector<int> VI;
typedef pair <int,int> ii;
typedef long long LL;
#define pb push_back
const int INF = 2147483647;

int n, tab[50005], bat[50005], i;

int go(int q) {
	int res = 0;
	bat[0] = tab[0];
	for (int i=1;i<n;i++) {
		bool gret = (i % 2 == q);
		if ((gret && tab[i] > bat[i - 1]) || (!gret && tab[i] < bat[i - 1])) {
			bat[i] = tab[i];
			continue;
		}
		if (gret) bat[i] = 10000000; else bat[i] = -10000000;
		res++;
	}
	return res;
}

int main() {
scanf("%d", &n);
for (i=0;i<n;i++) scanf("%d", &tab[i]);
printf("%d\n", min(go(1), go(0)));
return 0;
}