C :

#include <stdio.h>
int main() {
	int x,sum;
	while(scanf("%d",&x)!=EOF) {
		sum=x;
		while(x>=3) {
			sum+=x/3;
			x=x/3+x%3;
		}
		printf("%d\n",sum);
	}
	return 0;
}

C++ :

# include <iostream>
using namespace std;

int main()
{
	int n, j = 0, k;
	
	while(cin >> n)
	{
		int j = 0;
		k = n;
		while(n >= 3)
		{
			j += n / 3;
			n = n / 3 + n % 3;
		}
		cout << j + k << endl;
	}
	
	return 0;
}