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