#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int d;
    cin >> d;

    if(d <= 9){
        cout << d << endl;
    }else{
        d -= 9;
        if(d % 2 == 1){
            int ans = 1;
            while(d > 20){
                ans++;
                d -= 20;
            }
            cout << ans << endl;
        }else{
            cout << ((d + 18) % 20) / 2 << endl;
        }
    }

    return 0;
}