#include <bits/stdc++.h>
using namespace std;

int n, ans;

int main() {
  cin >> n;
  if(n < 10)
    cout << n << endl;
  else {
    n -= 9;
    if(n % 2)
      ans = (9 + (n + 1) / 2) / 10;
    else
      ans = (9 + (n + 1) / 2) % 10;
  }
  cout << ans << endl;
  return 0;
}