#include <iostream>
using namespace std;

int main()
{
	int n;
	double m;
	cin >> n;
	if (n>=30)
	{
		m = n * 1;
	}
	else if (n>=20 && n<=29)
	{
		m = n * 1.2;
	}
	else if (n>=10 && n<=19)
	{
		m = n * 1.5;
	}
	else
	{
		m = n * 1.8;
	}
	printf("%.1f",m);
}
/**************************************************************
	Problem: 1304
	User: xiaomingze
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/