package main

import (
	"fmt"
	"strconv"
)

func main() {
	var N, v, V, cnt uint64
	fmt.Scan(&N)
	ans := 0
	cnt = 1
	V = 1000000001
	v = V
	for N >= v {
		w := []byte(strconv.FormatUint(v, 10))
		// t := true
		// for i := 0; i < len(w)/2; i++ {
		// 	if w[i] != w[len(w)-1-i] {
		// 		t = false
		// 		break
		// 	}
		// }
		a := w[:len(w)/2]
		b := w[len(w)/2+len(w)%2:]
		for i := 0; i < len(b)/2; i++ {
			b[i], b[len(b)-1-i] = b[len(b)-1-i], b[i]
		}
		// log.Println(a, b)
		if string(a) == string(b) {
			ans++
		}
		// log.Println(N, v, t, N >= v)
		cnt++
		v = V * cnt
		// log.Println(v)
	}
	fmt.Println(ans)
}