#include<iostream>
#include<iomanip>
using namespace std;

int seq(double *x) {
	x[1] = x[0] * 2;
	for (int i = 2; i < 10; i + 2) {
		x[i] = x[i - 1] / 3;
		x[i + 1] = x[i] * 2;
	}
	int y=0;
	for (int i = 0; i < 10; i++) {
		y += x[i];
	}
	return y;
}

int main() {
	double d[10];
	while (cin >> d[0]) {
		cout << fixed << setprecision(9) << seq(d) << endl;
	}
	return 0;
}