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#include <bits/stdc++.h>
#define INF 1000000000
using namespace std;

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int n;
	cin >> n;
	int a[n], b[n], c[n]; //dane, od malejacego, od rosnacego
	int wynikb = 0, wynikc = 0;
	for(int i = 0; i < n; i++){
		cin >> a[i];
		b[i] = a[i];
		c[i] = a[i];
		if(i){
			if(i%2 == 0){
				if(a[i] >= b[i-1]) b[i] = -INF;
				if(a[i] <= c[i-1]) c[i] = INF;
			}else{
				if(a[i] <= b[i-1]) b[i] = INF;
				if(a[i] >= c[i-1]) c[i] = -INF;
			}
		}
		if(a[i] != b[i]) wynikb++;
		if(a[i] != c[i]) wynikc++;
	}
	cout << min(wynikb, wynikc);
	return 0;
}