#include<bits/stdc++.h>
using namespace std;
int main(){
	float s,q;
	cin>>s;
	if(s<=20){
		q=s*1.68;
	}
	if(s>20){
		q=s*1.98;
	}
	cout<<q;
	return 0;
}

/**************************************************************
	Problem: 1643
	User: huangcanwu
	Language: C
	Result: Compile Error
****************************************************************/