#include <iostream>
using namespace std;

int main() {
	int d;
	cin >>d;
	if(d<10){
		cout <<d<<endl;
	}
	else if(d%2==0){
		cout <<(d+10)/20;
	}
	else {
		cout<<((d+10)%20)/2<<endl;
	}
	
	return 0;
	
}