#include <bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	double price;
	
	if(n>=10){
	price=n*2.0;	
	}else{
    price=n*2.2;
	}
	cout<<fixed<<setprecision(1)<<price<<endl;
	return 0;
	
}
/**************************************************************
	Problem: 1303
	User: huanghao
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/