#include<bits/stdc++.h> using namespace std;

int main(){ freopen("age.in","r",stdin); freopen("age.out","w",stdout); int ren,s=0; long long mao; cin>>ren; if(ren<15){ cout<<'0'; return 0; }else if(ren>=15&&ren<24){ cout<<'1'; return 0; }else if(ren==24){ cout<<"2"; return 0; }else{ s=ren-24; s/=4; s+=2; cout<<s; } return 0; }