#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	
	auto solve = [](int n) {
		string N = to_string(n);
		vector dp(N.size() + 1, vector(2, vector(2, 0))); // [i][j][k] := 上 i 桁確定, j:max, k:leading-zero
		dp[0][1][1] = 1;
		REP(i, N.size()) REP(j, 2) REP(k, 2) {
			for (int l = 0; l < 10; l += 3) {
				if (j && N[i] < '0' + l) break;
				dp[i + 1][j && N[i] == '0' + l][k && l == 0] += dp[i][j][k];
			}
		}
		int res = 0;
		REP(i, 2) res += dp[N.size()][i][false];
		return res;
	};
	int ans = solve(N) - solve(min(99, N));
	ans += min(99, N) / 3 - 3;
	cout << ans << endl;
}