#include <bits/stdc++.h>
#include <cmath>
#include <bitset>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>pbds;
#define ll  long long  int
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define    gcd(a,b)         __gcd(a,b)
#define    lcm(a,b)        ((a*b)/gcd(a,b))
#define    pi               acos(-1.00)
const ll mod=1000000007;
 
void evan(int t) {
 ll n;cin>>n;
 if(n==2){
  cout<<1<<"\n";return;
 }
 if(n%3==1){
    ll ans=(n/3)-1;
    ans+=2;
    cout<<ans<<"\n";
 }
 else if(n%3==2){
   cout<<(n/3)+1<<"\n";
 }
 else{
  cout<<n/3<<"\n";
 }
}
signed main()
{
   ios_base::sync_with_stdio(false);
   cin.tie(NULL);
   cout.tie(nullptr);
    ll t=1;
 // cin>>t;
     for(int i=1;i<=t;i++){ 
         evan(i);
       }
}