#![allow(non_snake_case)]
#![allow(unused_imports)]
// use itertools::Itertools;
// use proconio::input;
// use proconio::marker::*;
use std::cmp::Reverse;
use std::collections::*;

fn main() {
    input! {
        n:usize,
    }

    const N: usize = 1_000_000_001;
    let mut ans = 0;
    for i in (1..).map(|i| i.to_string().chars().collect::<Vec<_>>()) {
        let x = i
            .iter()
            .chain(i.iter().rev())
            .collect::<String>()
            .parse::<usize>()
            .unwrap();
        let y = i
            .iter()
            .chain(i.iter().take(i.len() - 1).rev())
            .collect::<String>()
            .parse::<usize>()
            .unwrap();
        if N * x <= n {
            ans += 1;
        }

        if N * y <= n {
            ans += 1;
        } else {
            break;
        }
    }

    println!("{}", ans);
}

mod input{
    #[macro_export]
    macro_rules! input {
        (source = $s:expr, $($r:tt)*) => {
            let mut iter = $s.split_whitespace();
            input_inner!{iter, $($r)*}
        };
        ($($r:tt)*) => {
            let s = {
                use std::io::Read;
                let mut s = String::new();
                std::io::stdin().read_to_string(&mut s).unwrap();
                s
            };
            let mut iter = s.split_whitespace();
            input_inner!{iter, $($r)*}
        };
    }
    
    #[macro_export]
    macro_rules! input_inner {
        ($iter:expr) => {};
        ($iter:expr, ) => {};
    
        ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
            let $var = read_value!($iter, $t);
            input_inner!{$iter $($r)*}
        };
    }
    
    #[macro_export]
    macro_rules! read_value {
        ($iter:expr, ( $($t:tt),* )) => {
            ( $(read_value!($iter, $t)),* )
        };
    
        ($iter:expr, [ $t:tt ; $len:expr ]) => {
            (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
        };
    
        ($iter:expr, chars) => {
            read_value!($iter, String).chars().collect::<Vec<char>>()
        };
    
        ($iter:expr, usize1) => {
            read_value!($iter, usize) - 1
        };
    
        ($iter:expr, $t:ty) => {
            $iter.next().unwrap().parse::<$t>().expect("Parse error")
        };
    }
    
}