#include<bits/stdc++.h>
using namespace std;
int main()
{
	float n;
	cin>>n;
	if(n<=20.0) printf("%.2f",n*1.68);
	else printf("%.2f",n*1.98);







	return 0;
}

/**************************************************************
	Problem: 1643
	User: 21A
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/