#include<bits/stdc++.h>
using namespace std;
int main(){
int i;
cin>>i;
		if(i>=10)printf("%.1f",i*2.0);
		else printf("%.1f",i*2.2);
		
}
/**************************************************************
	Problem: 1303
	User: shenyue
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/