#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: zxh001
	Language: C
	Result: Compile Error
****************************************************************/