#include <cstdio>

int f[50505];

template <typename T> T min_of(T a, T b) { return a < b ? a : b; }

int compute(int *f, int n, bool up) {
  int mods = 0;
  for (int i = 1; i < n; ++i) {
    if((up && f[i] <= f[i-1]) || (!up && f[i] >= f[i -1])) {
      mods += 1;
      i +=1;
    } else {
      up = !up;
    }
  }
  return mods;
}

int main() {
  int N;
  scanf("%d", &N);
  for (int i = 0; i < N; ++i) {
    scanf("%d", &f[i]);
  }

  printf("%d\n", min_of(compute(f, N, true), compute(f, N, false)));

  return 0;
}