#pragma region Macros

#include <bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;
// using namespace __gnu_cxx;

#define TO_STRING(var) # var
#define pb emplace_back
#define int ll
#define endl '\n'

using ll = long long;
using ld = long double;
const ld PI = acos(-1);
const ld EPS = 1e-10;
const int INF = 1 << 30;
const ll INFL = 1LL << 62;
const int MOD = 998244353;
// const int MOD = 1000000007;

int ceil(int x, int y) {return (x > 0 ? (x + y - 1) / y : x / y);}
int POW(int x, int y) {
    if (y != (int)(y) or y < 0 or x != 0 && x != 1 && y > 64) {cout << "Error" << endl;return 0;}
    if (y == 0) return 1;
    if (y % 2 == 0) return POW(x * x, y / 2);
    return x * POW(x, y - 1);
}

__attribute__((constructor))
void constructor() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
}

#pragma endregion

signed main() {
	int N;
	cin >> N;

	if (N <= 110) {cout << 0 << endl; return 0;}

	int k = to_string(N).size();	
	int d = k / 3;

	bool flag = (k % 3 == 0);

	if (flag) {
		int ans = 0;
		string s = "";
		string t = to_string(N);

		vector<string> S(3);
		for (int i = 0; i < d; i++) {
			S[0] += t[i];
		}
		for (int i = d; i < 2 * d; i++) {
			S[1] += t[i];
		}
		for (int i = 2 * d; i < 3 * d; i++) {
			S[2] += t[i];
		}
		if (S[0] < S[1] or S[0] == S[1] && S[2] >= S[0]) {
			cout << stoll(S[0]) << endl;
			return 0;
		}

		for (int i = 0; i < d; i++) {
			s += t[i];
		}
		int n = stoll(s);
		cout << n - 1 << endl;
	} else {
		int ans = 1;
		for (int i = 0; i < d; i++) {
			ans *= 10LL;
		}
		cout << ans - 1 << endl;
	}
}