#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
using ll = long long;

int main(void){
  vector<int> two;
  for(int i=1; i<9; i++)for(int j=i+1; j<=9; j++) two.push_back(i*10+j);
  //for(auto p:two) cout << p << ' '; cout << endl;
  int n; cin >> n; n--;
  int m=two.size();
  int turn=n/m, id=n%m, r=two[id]%10;
  //cout << turn << ' ' << id << ' ' << r << endl;
  cout << two[id] << string(turn, '0'+r);
  return 0; 
}