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#include <cstdio>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <cassert>
#include <limits.h>

using namespace std;

typedef long long LL;
typedef long double LD;

typedef vector<int> VI;
typedef pair<int,int> PII;
#define REP(i,n) for(int i=0;i<(n);i++)
#define FOR(i,a,b) for(VAR(i,a);i<=(b);++i)
#define FORD(i,a,b) for(VAR(i,a);i>=(b);--i)
#define FORE(a,b) for(VAR(a,(b).begin());a!=(b).end();++a)
#define VAR(a,b) __typeof(b) a=(b)
#define SIZE(a) ((int)((a).size()))
#define ALL(x) (x).begin(),(x).end()
#define CLR(x,a) memset(x,a,sizeof(x))
#define ZERO(x) memset(x,0,sizeof(x))
#define S(t,i) scanf("%" ## t, &i)
#define SI(i) scanf("%d", &i)

int n, m;

int main() {
    ios_base::sync_with_stdio(0);
    
    SI(n);
    int w[2] = {0, 0};
    int a[2] = {1, -1};
    SI(m);
    int prev[2] = {m, m};
    
    FOR(i, 2, n) {
        SI(m);
        REP(ii, 2) {
            if (m >= prev[ii] && a[(i+ii) % 2] < 0) {
                prev[ii] = -10000000;
                w[ii]++;
            } else if (m <= prev[ii] && a[(i+ii) % 2] > 0) {
                prev[ii] = 10000000;
                w[ii]++;
            } else {
                prev[ii] = m;
            }
        }
    }
    //printf("%d %d\n", w[0], w[1]);
    printf("%d\n", min(w[0], w[1]));
    
    return 0;
}