#include <bits/stdc++.h>


using namespace std;
typedef long long ll;

#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VP vector<pair<int,int>>
#define VPP vector<pair<int,pair<int,int>>>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define VB vector<bool>
#define VVB vector<vector<bool>>
#define fore(i,a) for(auto &i:a)
typedef pair <int, int> P;
template<typename T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }

const int  INF = 1 << 29;
const ll INFL = 1LL << 60;
const ll mod = 998244353;

int ans = 0;
ll n;

void dfs(ll a) {
	if (10 <= a && a <= n) {
		ans++;
	}
	if (a > n)return;
	dfs(a * 10);
	dfs(a * 10 + 3);
	dfs(a * 10 + 6);
	dfs(a * 10 + 9);
}

int main(){

	
	cin >> n;


	FOR(i, 10, min(100, (int)n + 1)) {
		if (((i % 10) + (i / 10)) % 3 == 0) {
			if ((i % 10) % 3 != 0 && (i / 10) % 3 != 0) {
				if (i % 3 == 0) {
					ans++;
				}
			}
		}
	}
	dfs(3);
	dfs(6);
	dfs(9);
	cout << ans << endl;
}