#include<bits/stdc++.h>
using namespace std;
int main(){
	int g;
	float q;
	cin>>g;
	if(g>=10){
		q=g*2;
	}else{
		q=g*2.2;
	}
	printf("%.1f",q);
	return 0;
}

/**************************************************************
	Problem: 1303
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/