#include <bits/stdc++.h>  

using namespace std;

#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define repr(i, j) for(int i = j; i >= 0; --i)
#define INF (1 << 30)
#define MOD 1e9 + 7

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;

int main() {
	ll N;
	scanf("%lld", &N);
	ll ans = 0, a = 1e9 + 1, add = 1e9 + 1;
	while(1) {
		if(a <= N) ++ans;
		else break;
		if(ans % 9 == 0) {
			a = add * 10;
			add *= 10;
		}
		else a += add;
	}
	printf("%lld\n", ans);
	return 0;
}