#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);
	return 0;
	}
/**************************************************************
	Problem: 1303
	User: ljl2
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/