/* Topcoder SRM 699, D2, 500-pointer: LastDigit.
 * James S. Plank
 * Fri Nov 25 11:20:03 EST 2016
 */

#include <string>
#include <map>
#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;

class LastDigit {
  public:
    long long findX(long long S);
};

long long LastDigit::findX(long long S)
{
  long long T;          /* T is the biggest number <= S with all repeated digits. */
  long long I;          /* I is the first digit of T with all zeros. */
  long long RV;         /* This is the return value of the recursive call */

  string SS;            /* The string version of S. */
  string ST;            /* The string version of T. */
  string SI;            /* The string version of I. */
  string SRV;           /* The string version of RV. */

  char buf[50];         /* This is to convert long long's to strings. */
  int i;

  /* Base case. */

  if (S < 10) return S;

  /* Create string version of S. */

  sprintf(buf, "%lld", S);
  SS = buf;

  /* Create T from SS.  If it's too big, the either subtract all 1's from it, 
     or make it be all 9's, and one digit smaller. */

  ST = buf;
  for (i = 1; i < ST.size(); i++) ST[i] = ST[0];
  if (ST > SS) {
    if (ST[0] != '1') {
      for (i = 0; i < ST.size(); i++) ST[i]--;
    } else {
      for (i = 0; i < ST.size(); i++) ST[i] = '9';
      ST.pop_back();
    }
  }

  /* Now, create SI, and convert SI and ST back to I and T */

  SI = ST;
  for (i = 1; i < SI.size(); i++) SI[i] = '0';
  sscanf(ST.c_str(), "%lld", &T);
  sscanf(SI.c_str(), "%lld", &I);

  /* Make the recursive call, and check to make sure that the return
     value is not too big.  */

  RV = findX(S-T);
  if (RV != -1) {
    sprintf(buf, "%lld", RV);
    SRV = buf;
    if (SRV.size() == ST.size()) RV = -1;
  }

  /* If the return value is ok, then add I, and you're done. */

  if (RV != -1) RV += I;
  return RV;
}