#include<bits/stdc++.h>
using namespace std;
int main(){
	float a,f;
	cin>>a;
	if(a>=10){
		f=a*2;
		printf("%.1f",f);
	}else{
		f=a*2.2;
		printf("%.1f",f);
	}
}
/**************************************************************
	Problem: 1303
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/