#include<bits/stdc++.h>
using namespace std;
int main(){
	double q,n;
	cin>>n;
	if(n<=20) q=n*1.68;
	else q=n*1.98;
	cout<<fixed<<setprecision(2)<<q<<endl;
	return 0;
}

/**************************************************************
	Problem: 1643
	User: admin
	Language: C++
	Result: Accepted
	Time:23 ms
	Memory:2072 kb
****************************************************************/