#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <functional>
#include <set>
#include <sstream>
#include <map>
#include <queue>

using namespace std;
 
int main()
{
	double a;
	while(cin>>a){
		printf("%.10f\n",(81+162+54+108+36+72+24+48+16+32)*a/81);
	}


	return 0;
}