#include <bits/stdc++.h>
using namespace std;
int n,q[100000000];
int f(int a)
{
	if(q[a]) return q[a];
	if(a>=3)
	{
		q[a]=f(a/3+a%3)+a/3;
		return f(a/3+a%3)+a/3;
	}
	q[a]=0;
	return 0;
}
int main()
{
	cin >> n;
	int l=0,r=n,mid=n/2;
	while(l<r)
	{
		if(f(mid)+mid>n)
		{
			r=mid;
			mid=(l+r)/2;
		}
		else if(f(mid)+mid<n)
		{
			l=mid;
			mid=(l+r)/2;
		}
		else
		{
			cout << mid;
			return 0;
		}
	}
	cout << mid;
	return 0;
}