import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.io.PrintWriter
import java.util.*

fun PrintWriter.solve(sc: FastScanner) {
    val n = sc.nextInt()
    val lst = mutableListOf<Int>()
    for (i in 10..99) {
        if (i % 3 == 0) lst.add(i)
    }
    val stack = Stack<String>()
    stack.add("3")
    stack.add("6")
    stack.add("9")
    while (stack.count() > 0) {
        val s = stack.pop()
        val m = s.toInt()
        if (m >= 100) {
            lst.add(m)
        }
        if (s.length < 9) {
            stack.add(s + "3")
            stack.add(s + "6")
            stack.add(s + "9")
            stack.add(s + "0")
        }
    }
    println(lst.filter { it <= n }.count())
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve(FastScanner(System.`in`))
    writer.flush()
}

class FastScanner(s: InputStream) {
    private var st = StringTokenizer("")
    private val br = BufferedReader(InputStreamReader(s))

    fun next(): String {
        while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())

        return st.nextToken()
    }

    fun nextInt() = next().toInt()
    fun nextLong() = next().toLong()
    fun nextLine() = br.readLine()
    fun nextDouble() = next().toDouble()
    fun ready() = br.ready()
}