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#include <bits/stdc++.h>

using namespace std;


const int MAXN = 50010;

int A[MAXN];
int DP[MAXN][2];


int solve(int n) {
  int out = 0;
  vector<int> DP(n + 1);
  DP[1] = 0;
  int s = 1;

  for (int i = 2; i <= n; i++) {
    if (A[i] * s > A[i - 1] * s) {
      DP[i] = DP[i - 1];
    } else if (i == 2) {
      DP[i] = 1;
    } else {
      DP[i] = 1 + min(DP[i - 1], DP[i - 2]);
    }
    s = -s;
  }
  return DP[n];
}


int main() {
  int n;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", A + i);

  for (int i = 2; i <= n; i++) {
    for (int j = 0; j < 2; j++) {
      int s = j == 0 ? 1 : -1;
      if (A[i] * s > A[i - 1] * s) {
        DP[i][j] = DP[i - 1][1 - j];
      } else if (i == 2) {
        DP[i][j] = 1;
      } else {
        DP[i][j] = 1 + min(DP[i - 1][1 - j], DP[i - 2][j]);
      }
    }
  }

  printf("%d\n", min(DP[n][0], DP[n][1]));
}