//https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 より
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_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_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, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

//

fn dfs(v: u64, k: u64, a: &mut Vec<u64>) {
    if k > 2 {
        a.push(v);
    }
    if k >= 8 {
        return;
    }
    for d in [0, 3, 6, 9].iter() {
        dfs(10 * v + *d, k + 1, a);
    }
}

fn run() {
    input! {
        n: u64,
    }
    let mut a = vec![];
    for i in 1..10 {
        for j in 0..10 {
            if (i + j) % 3 == 0 {
                a.push(10 * i + j);
            }
        }
    }
    for s in [3, 6, 9].iter() {
        dfs(*s, 1, &mut a);
    }
    a.sort();
    a.dedup();
    let ans = a.iter().filter(|a| **a <= n).count();
    println!("{}", ans);
}

fn main() {
    run();
}