import scala.collection.mutable.*
import scala.io.StdIn.*
import scala.util.chaining.*
import scala.math.*
import scala.reflect.ClassTag
import scala.util.*
import scala.annotation.tailrec
import scala.collection.mutable

extension (value: Int)
  def toTriple: Long = value.toString.pipe(s => (s + s + s).toLong)
@main def main =
  val n = readLine.toLong
  var min = 0
  var max = 100000
  while min < max do
    val mid = (min + max) >>> 1
    if mid.toTriple <= n then
      min = mid + 1
    else
      max = mid
  println(max - 1)