#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: ccf
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/