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#include <bits/stdc++.h>

using namespace std;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);

  int n;
  cin >> n;
  vector<int> arr1(n); 
  vector<int> arr2(n);

  for(int i = 0; i < n; i++){
    cin >> arr1[i];
  }

  arr2 = arr1;

  int res1= 0, res2 = 0;
  bool shouldIncrease = true;
  for(int i = 0; i < n-1; i++){
    if(shouldIncrease && arr1[i] >= arr1[i+1]){
      res1++;
      arr1[i+1] = INT_MAX;
    }else if(!shouldIncrease && arr1[i] <= arr1[i+1]){
      res1++;
      arr1[i+1] = INT_MIN;
    }else{
    }
    shouldIncrease = !shouldIncrease;
  }
  shouldIncrease = false;
  for(int i = 0; i < n-1; i++){
    if(shouldIncrease && arr2[i] >= arr2[i+1]){
      res2++;
      arr2[i+1] = INT_MAX;
    }else if(!shouldIncrease && arr2[i] <= arr2[i+1]){
      res2++;
      arr2[i+1] = INT_MIN;
    }
    shouldIncrease = !shouldIncrease;
  }
  cout << min(res1,res2)<< '\n';
  return 0;
}