#include <iostream>
 
//https://p...content-available-to-author-only...j.com/problems/AL_30_03/
using namespace std;
 
int main(){
std::ios_base::sync_with_stdio(false);
cin.tie(NULL);
//cout.tie(NULL);
 
unsigned long long liczbacyfr;
while(cin>>liczbacyfr){
    unsigned long long pot, ile, stron, i, c=19;
    ile=stron=0;
    pot=i=1;
 
    while(ile<=liczbacyfr && i<c){
    	ile+=i*9*pot; //ile znakow sumarycznie
    	stron+=9*pot; //liczba stron sumarycznie
    	i++;
    	pot*=10;
    	//cout<<pot<<" - "<<i-1<<endl;
    }
 
    if(i<c){ //skompensuj do tylu
    	unsigned long long roznica=ile-liczbacyfr;
        roznica += (i-1 - roznica%(i-1))%(i-1);
    	cout<<stron - ((roznica)/(i-1))<<'\n';
    } else { // c=19 skompensuj do przodu
    	cout<<stron + ((liczbacyfr - ile)/c)<<'\n'; //189 i*pot
 
    }
 
} //while 
return 0;
}

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