#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
using namespace std;

typedef long long ll;

ll mod_pow(ll x, ll n, ll mod) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % mod;
        x = x * x % mod;
        n >>= 1;
    }
    return res;
}
int main() {
    int N, ans = 0;
    cin >> N;
    for (int i = 10; i < 100; i++) {
        if (i > N) {
            cout << ans << "\n";
            return 0;
        }
        if (i % 3 == 0) ans++;
    }
    for (int i = 16; i < 1048576; i++) {
        ll x = 0, y = 1, z = i;
        while (z > 0) {
            x += y * 3 * (z % 4);
            y *= 10;
            z /= 4;
        }
        //cout << x << "\n";
        if (x > N) {
            cout << ans << "\n";
            return 0;
        }
        ans++;
    }
}