#include <iostream>
#include <cmath>
#include <stdio.h>

int main(void)
{
	double N;

	std::cin >> N;
	
	if(N == 0)
	{
		std::cout << 4 << std::endl;
	}
	else
	{
		double AN = 3 * pow(0.75, N - 1);
		
		printf("%10f\n", AN);
	}

	return 0;
}