#include <string>
#include <vector>
#include <iostream>
using namespace std;
int main() {
	int N;
	cin >> N;
	if (N <= 99) {
		int cnt = 0;
		for (int i = 10; i <= N; ++i) {
			string str = to_string(i);
			bool ok = true;
			for (int j = 0; j < str.size(); ++j) {
				for (int k = 0; k < j; ++k) {
					if ((str[j] + str[k]) % 3 != 0) {
						ok = false;
					}
				}
			}
			if (ok) ++cnt;
		}
		cout << cnt << endl;
	}
	else {
		int cnt = 0;
		for (int i = 10; i <= 99; ++i) {
			string str = to_string(i);
			bool ok = true;
			for (int j = 0; j < str.size(); ++j) {
				for (int k = 0; k < j; ++k) {
					if ((str[j] + str[k]) % 3 != 0) {
						ok = false;
					}
				}
			}
			if (ok) ++cnt;
		}
		for (int i = 3; i <= 9; ++i) {
			int mul = 1;
			for (int j = 0; j < i; ++j) {
				mul *= 4;
			}
			for (int j = 0; j < mul; ++j) {
				string str; int x = j;
				for (int k = 0; k < i; ++k) {
					str += char((x % 4) * 3 + '0');
					x /= 4;
				}
				if (str[0] != '0' && stoi(str) <= N) {
					++cnt;
				}
			}
		}
		cout << cnt << endl;
	}
	return 0;
}