#include <bits/stdc++.h>
#define all(vec) vec.begin(),vec.end()
using namespace std;
using ll=long long;
using P=pair<int,int>;
const ll INF=1LL<<30;
const ll LINF=1LL<<61;
const double eps=1e-9;
const ll MOD=1e9+7;
int main(){
    int d;cin>>d;
    if(d<10){
        cout<<d<<endl;
    }else{
        if(d%2==0){
            cout<<1+(d-10)/20<<endl;
        }else{
            cout<<((d-10)%20)/2<<endl;
        }
    }
}