#include <iostream>
using namespace std;

int main()
{
	int n;
	double m;
	cin >> n;
	if (n >= 10)
	{
		m = n*2; 
	}
	else
	{
		m = n *2.2;
	}
	printf("%.1f",m);
}
/**************************************************************
	Problem: 1303
	User: xiaomingze
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/