#include<bits/stdc++.h>
using namespace std;
#define fs first
#define sc second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
#define RALL(A) A.rbegin(),A.rend()
typedef long long LL;
typedef pair<LL,LL> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
const LL mod=1000000007;
const LL LINF=1LL<<62;
const int INF=1<<30;
int dx[]={1,0,-1,0,-1,1,1,-1};
int dy[]={0,1,0,-1,-1,-1,1,1};


LL ans;
LL n;
set<LL> st;

void dfs(LL k, LL p){
    if(n < k || p > n * 10) return ;
    if(100 <= k && k % 3 == 0){
        st.insert(k);
    }
    dfs(k + 0 * p, p * 10);
    dfs(k + 3 * p, p * 10);
    dfs(k + 6 * p, p * 10);
    dfs(k + 9 * p, p * 10);
}


int main(){
    cin >> n;
    if(n < 100){
        for (int i = 12; i <= n; i+=3) {
            if(((i % 10) + (i / 10))%3 == 0) ans++;
        }
    }
    else{
        for (int i = 12; i < 100; i+=3) {
            if(((i % 10) + (i / 10))%3 == 0) ans++;
        }
        dfs(0, 1);
        ans += st.size();
    }
    cout << ans << endl;
    return 0;
}