#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    int x = n;
    int i=0;
    while(n!=0){
        n = n-3;
        i++;
    }
    int j = 0;
    while(x!=0){
        x = x-2;
        j++;
    }
    if(i<j){
        cout<<i;
    }
    else if(j<i){
        cout<<j;
    }
}