#[allow(unused_imports)]
use std::cmp;
use std::fs::File;
use std::io::Read;

#[allow(dead_code)]
fn pow_speedy_with_mod(mut p: i64, mut q: i64, m: i64) -> i64 {
    p %= m;
    let mut r = p;
    let mut ret: i64 = 1;
    while q > 0 {
        ret *= if q % 2 == 1 { r } else { 1 };
        r *= r;
        r %= m;
        q /= 2;
        ret %= m;
    }
    return ret;
}

fn comb(n: usize, k: usize, m: i64, frac: &[i64], frac_inv: &[i64]) -> i64 {
    let mut ret = 1i64;
    if n < k {
        return 0;
    }
    ret *= frac[n] * frac_inv[n - k];
    ret %= m;
    ret *= frac_inv[k];
    ret %= m;
    ret
}

fn main() {
    let inputstatus = 1;

    let mut buf = String::new();
    let filename = "inputrust.txt";

    if inputstatus == 0 {
        let mut f = File::open(filename).expect("file not found");
        f.read_to_string(&mut buf)
            .expect("something went wrong reading the file");
    } else {
        std::io::stdin().read_to_string(&mut buf).unwrap();
    }

    let mut iter = buf.split_whitespace();

    let n: i32 = iter.next().unwrap().parse().unwrap();
    let mut search = vec![3, 6, 9];
    let mut new_search = Vec::<i32>::new();

    let mut comp_3 = Vec::<i32>::new();

    for i in 10..100 {
        if i % 3 == 0 && (i % 10) % 3 != 0 {
            comp_3.push(i);
        }
    }

    for _ in 0..8 {
        for v in &search {
            for u in [0, 3, 6, 9].iter() {
                comp_3.push(10 * v + u);
                new_search.push(10 * v + u);
            }
        }

        search.clear();
        search = new_search;
        new_search = Vec::<i32>::new();
    }
    let mut ans = 0;
    for v in comp_3 {
        if v <= n {
            ans += 1;
        }
    }
    println!("{}", ans);
    // let n = iter.next().unwrap().parse().unwrap();

    // println!("{}", n);
    // println!("{:?}", cum_num);
}