#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: lyy002
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/