#![allow(unused_imports)]
#![allow(non_snake_case)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let n = read::<i64>();
    let mut ans = 0;
    for i in 10..min(100, n + 1) {
        if i % 3 == 0 && (i % 10) % 3 != 0 {
            ans += 1;
        }
    }

    let n = format!("{}", n);
    let mut dp = vec![vec![0i64; 2]; n.len() + 1];
    dp[0][0] = 1; // pos, less

    for (i, c) in n.chars().enumerate() {
        for j in 0..2 {
            let lim = if j == 1 { 9 } else { c.to_digit(10).unwrap() };
            for l in 0..lim + 1 {
                if l % 3 != 0 {
                    continue;
                }
                let idx1 = if j == 1 || l < lim { 1 } else { 0 };
                dp[i + 1][idx1] += dp[i][j];
            }
        }
    }

    for j in 0..2 {
        ans += dp[n.len()][j];
    }

    println!("{}", ans - 4);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}