#include <iostream>
#include <vector>
#include<iomanip>
#include<functional>
#include<algorithm>
#include<deque>
#include<math.h>
#include<set>
#include<string>
#include<queue>
#include<complex>
#include<numeric>
#include<stack>
#include<map>
using namespace std;
#define rep(i,n) for(ll i = 0;i<n;i++)
#define req(i,n) for(ll i = 1;i<=n;i++)
#define rrep(i,n) for(int i = n-1;i>=0;i--)
#define ALL(a) a.begin(),a.end()
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; }
typedef unsigned long long ll;
typedef long double ld;
int dfs(int n, int now,int cnt) {
    int res = 0;
    if (cnt == 9) {
        if (now > 10&&now <= n) {
            return 1;
        }
        else return 0;
    }res += dfs(n, now * 10, cnt + 1);
    res += dfs(n, now * 10 + 3, cnt + 1);
    res += dfs(n, now * 10 + 6, cnt + 1);
    res += dfs(n, now * 10 + 9, cnt + 1);
    return res;
}
int main() {
    int n,ans = 0; cin >> n;
    if (n < 100) {
        for (int i = 10; i <= n; i++) {
            if (i % 3 == 0) ans++;
        }cout << ans << endl;
    }
    else {
        for (int i = 10; i <100; i++) {
            if (i % 3 == 0) ans++;
        }
        cout << ans + dfs(n, 0, 0)-12 << endl;
    }
}