#include <iostream>
#include <iomanip>
#include <vector>
#include <utility>
#include <map>
#include <algorithm>
#include <queue>
#include <cmath>
#include <numeric>
#include <set>

using namespace std;
struct aaa{aaa(){cin.tie(nullptr); ios::sync_with_stdio(false); cout<<fixed<<setprecision(20);};}aaa;
template <class T>ostream &operator<<(ostream &o,const vector<T>&v){o<<"{";for(int i=0;i<(int)v.size();i++)o<<(i>0?", ":"")<<v[i];o<<"}";return o;}
#define debug(v) {cerr<<"\033[1;36m[debug]\033[m "<<#v<<" : "<<v<<endl;}

using int64 = long long;

void dfs(int64 i, const int& n, int& ans) {
    if (i > n) return;
    if (i >= 100) ans++;
    dfs(i*10+0, n, ans);
    dfs(i*10+3, n, ans);
    dfs(i*10+6, n, ans);
    dfs(i*10+9, n, ans);
};

int main() {
    int n;
    cin >> n;

    int ans = 0;
    if (n >= 100) {
        ans += 100 / 3 - 3;
    } else {
        ans += n / 3 - 3;
    }

    dfs(3,n,ans);
    dfs(6,n,ans);
    dfs(9,n,ans);

    cout << ans << endl;
}