#include<bits/stdc++.h>
using namespace std;
int main(){ 
	int a;
	double ans;
	cin>>a;
	if(a>=10) ans=a*2;
	else ans=a*2.2;	
	printf("%.1f",ans);
} 



/**************************************************************
	Problem: 1303
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/