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

int main(){
	int n;
	float a;
	cin>>n;
	if(n>=10){
		a=n*2;
		printf("%.1f",a);
	}else{
		a=n*2.2;
		printf("%.1f",a);
	}
}

/**************************************************************
	Problem: 1303
	User: linzihang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/