#include<bits/stdc++.h>
using namespace std;
int main() {
	float a;
	cin>>a;
	if(a<=20) printf("%.2f",a*1.68);
	else printf("%.2f",a*1.98);
}
/**************************************************************
	Problem: 1643
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/