#include<iostream>
using namespace std;
int main(){
    int N;
    cin>>N;
    int operation=0;
    while(N>0){
        if(N%3==0){
            N=N-3;
            operation++;
        }
        else{
            N=N-2;
            operation++;
        }
    }
    cout<<operation<<endl;

return 0;
}