#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: chenmingyu
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/