#include<bits/stdc++.h>
using namespace std;
int main()
{
int n;
cin>>n;
if(n>=10)printf("%.1f",n*2.0);
else printf("%.1f",n*2.2);
 
 
 return 0;
 }
 
/**************************************************************
	Problem: 1303
	User: binzicheng1
	Language: C
	Result: Compile Error
****************************************************************/