#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: lijinkai
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/