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#include <bits/stdc++.h>

using namespace std;

int n;
int t[1000006];
int pom[1000006];
int maks = 1000000000;

int calc(bool greater) {
  for (int i = 0; i < n; ++i) {
    pom[i] = t[i];
  }

  int res = 0;
  for (int i = 1; i < n; ++i) {
    if (greater) {
      if (pom[i] <= pom[i - 1]) {
        pom[i] = maks;
        ++res;
      }
    } else {
      if (pom[i] >= pom[i - 1]) {
        pom[i] = -maks;
        ++res;
      }
    }
    greater = !greater;
  }
  return res;
}

int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; ++i) {
    scanf("%d", &t[i]);
  }
  printf("%d\n", min(calc(true), calc(false)));
}