#include "bits/stdc++.h"
using namespace std;
#define ll long long int

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    if (n/10==0) cout << n << endl;
    else if (n%2==0) cout << (n-10)/20+1 << endl;
    else cout << ((n-10)%20)/2 << endl;
    return 0;
}