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

	return 0;
}

/**************************************************************
	Problem: 1643
	User: lvrenxiang
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/