#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define REPO(i, n) for(int i = 1;i <= n;i++)
#define ll long long
#define INF 999999999
#define MINF -999999999

int main() {
	int n, a[110] = {}, b = 10;
	cin >> n;
	REPO(i, 9) a[i] = i;
	for (int i = 10; i < 102; i = i + 2) {
		a[i] = (10 + (i - 10) / 2) / 10;
		a[i + 1] = (10 + (i - 10) / 2) % 10;
	}
	cout << a[n];

}