#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a;
	double b,c;
	cin>>a;
	if(a>=30)
	{
		b=1;
	}else if(a>=20&&a<=29)
	{
		b=1.2;
	}else if(a>=10&&a<=19)
	{
		b=1.5;
	}else if(a<10)
	{
		b=1.8;
	}
	printf("%.1f",a*b);
	return 0;
}

/**************************************************************
	Problem: 1304
	User: lzc
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/