#include<bits/stdc++.h>
using namespace std;
int main(){
    int N; cin>>N;
    int T_operation = 0;
    while(N--){
        if(N%3 == 0){
            N-=3;
        }
        else{
            N-=2;
        }
        T_operation++;
    }
    cout<<T_operation<<endl;
    
}