#include<bits/stdc++.h>
using namespace std;
#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define ll long long int
#define fr for(int i=0;i<n;i++)
#define tc int t;  cin >> t;  while(t--)
#define yes cout<<"YES"<<endl
#define no cout<<"NO"<<endl

int main()
{
    fastio;
    int n;
    cin>>n;

    if(n%3 == 2)cout<<n/3 +1<<endl;
    else cout<<n/3<<endl;

}