#include<bits/stdc++.h>
using namespace std;
int main()
{
	double n;
	cin>>n;
	if(n<=20) n=n*1.68;
	else n=n*1.98;
	printf("%.2f",n);
	return 0;
}

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