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#include <iostream>
#include <algorithm>
#include <vector>
   
#define push push_back
#define ll long long
   
using namespace std;

int proc(int n, vector<int> T, int trueVal, int falseVal) {
    // cout << "PROCEDURE\n";

    vector<int> vertice(n+1); // -1, 0, 1
   int result = 0;

   for(int i = 1; i < n; i++) {
       if(i%2 == trueVal) {
            if((vertice[i] == 1 || vertice[i-1] == -1) ){
               continue;
           }
           if(T[i] >= T[i-1]) {
            //    cout << i << " | " << " A\n";
               result++;
               vertice[i] = 1;
           }
       }else if(i%2 == falseVal) {
           if((vertice[i] == -1 || vertice[i-1] == 1) ){
               continue;
           }

           if(T[i] <= T[i-1]) {
                // cout << i << " | " << " B\n";

               result++;
               vertice[i] = -1;
           }
       }
   }
   return result;
}
   
int main() {
   ios_base::sync_with_stdio(0);
   cin.tie(0);
   
   int n;
   cin >> n;

   vector<int> T(n);
   for(int i = 0; i < n; i++) {
       cin >> T[i];
   }  
    int a = proc(n, T, 1, 0);
    int b = proc(n, T, 0, 1);

    // cout << a << " " << b << "\n";

    cout << min(a,b) << "\n";
}