#include "bits/stdc++.h"
#include<unordered_map>
#include<unordered_set>
#pragma warning(disable:4996)
using namespace std;
using ld = long double;
template<class t>
using table = vector<vector<t>>;
const ld eps=1e-9;

//// < "d:\d_download\visual studio 2015\projects\programing_contest_c++\debug\a.txt" > "d:\d_download\visual studio 2015\projects\programing_contest_c++\debug\b.answer"

int main() {
	ld a;
	while (cin >> a) {
		ld ans = a*7.81481481;
		cout << setprecision(22)<<fixed<<ans << endl;
		
	}
	return 0;
}