#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 10010;
int n;
int main()
{
cin>>n;
int sum=n;
while(n>=3)
{
int x=n/3;
int y=n%3;
sum+=x;
n=x+y;
}
cout<<sum;
return 0;
}