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#include <bits/stdc++.h>
#define ft first
#define sc second
#define pb push_back
#define FOR(i,n) for(int i=0; i<n; i++)
#define watch(x) cout << (#x) << " == " << (x) << endl
typedef long long ll;
typedef long double ld;
using namespace std;
const ll N = 5e4;
int dp[N+5][2]; //0 +/-
int tab[N+5];

int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);

int n;
cin>>n;
for (int i=1; i<=n; i++){
  cin>>tab[i];
}

dp[0][0]=0;
dp[0][1]=0;
dp[0][2]=0;

int mmin;

//-+
for (int i=1; i<=n; i++){
  dp[i][0] = dp[i-1][1];
  if ( (i%2==1 && (tab[i-1] > tab[i])) || (i%2==0 && (tab[i-1] < tab[i])) ){
    dp[i][0] = min(dp[i][0], dp[i-1][0]);
  }
  dp[i][1] = 1 + min(dp[i-1][0], dp[i-1][1]);
}
mmin = min(dp[n][0], dp[n][1]);

//-+
for (int i=1; i<=n; i++){
  dp[i][0] = dp[i-1][1];
  if ( (i%2==1 && (tab[i-1] < tab[i])) || (i%2==0 && (tab[i-1] > tab[i])) ){
    dp[i][0] = min(dp[i][0], dp[i-1][0]);
  }
  dp[i][1] = 1 + min(dp[i-1][0], dp[i-1][1]);
}
mmin = min({mmin, dp[n][0], dp[n][1]});

cout<<mmin;

return 0;
}