03-Philatelist-Ram.cpp

#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
    ll stones,present;
        cin>>stones;
        present=0;
        present=2*(stons/3);
        if(stones%3>0)
            present++;
        cout<<present<<endl;
    
    return 0;
}