#include<bits/stdc++.h>
using namespace std;
int main(){ 
	int a;
	double ans;
	cin>>a;
	if(a>=30) ans=a*1;
	else if(a>=20&&a<=20)ans=a*1.2;	
	else if(a>=10&&a<=19)ans=a*1.8;	
	else if(a<10)ans=a*1.8;	
	printf("%.1f",ans);
} 



/**************************************************************
	Problem: 1304
	User: zhuangsongyu
	Language: C++
	Result: Wrong Answer
****************************************************************/