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#include <stdio.h>
#define MAX (1000*1000*1000)
#define MIN (-1*MAX)


int main() {
  int ret1 = 0, ret2 = 0;
  int n, in[50000];
  scanf("%d", &n);
  for(int i = 0; i < n; i++) {
    scanf("%d", &(in[i]));
  }
  int prev = MIN;
  for(int i = 0; i < n; i++) {
    if(i % 2 == 0 && in[i] <= prev) {
      ret1++;
      prev = MAX;
    } else if(i % 2 == 1 && in[i] >= prev) {
      ret1++;
      prev = MIN;
    } else {
      prev = in[i];
    }
  }
  prev = MAX;
  for(int i = 0; i < n; i++) {
    if(i % 2 == 1 && in[i] <= prev) {
      ret2++;
      prev = MAX;
    } else if(i % 2 == 0 && in[i] >= prev) {
      ret2++;
      prev = MIN;
    } else {
      prev = in[i];
    }
  }

  printf("%d", (ret1 < ret2 ? ret1 : ret2));
  return 0;
}