#include <bits/stdc++.h> 
using namespace std;
int main() {
	int a;
	cin>>a;
	if(a>=10)
		printf("%.1f",a*2.0);
	else printf("%.1f",a*2.2);
}  
	
	


/**************************************************************
	Problem: 1303
	User: zhuangwenya
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/