#include<bits/stdc++.h>
using namespace std;
int main(){
	float n,f;
	cin>>n;
	if(n<20){
		f=n*1.68;
		printf("%.2f",f);
	}else{
		f=n*1.98;
		printf("%.2f",f);
	}
}
/**************************************************************
	Problem: 1643
	User: wangyiyang
	Language: C++
	Result: Wrong Answer
****************************************************************/