{
  p = ($2 -$1) < 0 ? -1 : 1
  safe = 1
  for (i=2;i<=NF;i++) {
    d = ($i - $(i-1))
    q = d < 0 ? -1 : 1
    if (p != q || d>3 || d<-3 || d == 0) {
      safe = 0
      break
    } 
  }
  #print NR, $0 , p, safe
  S += safe
}
END {
  print S
}