#include<bits/stdc++.h>
using namespace std;

int main(){
	int n;
	cin>>n;
	if(n>=10){
		printf("%.1f",2.0*n);
	}else{
		printf("%.1f",2.2*n);
	}
	return 0;
}

/**************************************************************
	Problem: 1303
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:47 ms
	Memory:2072 kb
****************************************************************/