#include<bits/stdc++.h>
using namespace std;
int main(){
	float a,p;
	cin>>a;
	if (a<=20){
		p=a*1.68;
		printf("%.2f",p);
	}
	else {
		p=a*1.98;
		printf("%.2f",p);
	}
	return 0;
}
/**************************************************************
	Problem: 1643
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/