// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <stdio.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}

int solve(int cur,int n){
    int res=0;
    if(cur>n)return 0;
    if(cur>100){res++;}
    if(cur)res+=solve(10*cur,n);
    res+=solve(10*cur+3,n)+solve(10*cur+6,n)+solve(10*cur+9,n);
    return res;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n; cin >> n;
    int res=0;
    for(int i=12;i<=min(n,100);i+=3)res++;
    if(n<=100){
        printf("%d\n",res);
    }
    else{
        res+=solve(0,n);
        printf("%d\n",res);
    }
}