#include<bits/stdc++.h>
using namespace std;
int main(){ 
	int n;
	cin>>n;
	float a;
	if(n>=10){
		a=2.0*n;
	}else{
		a=2.2*n;
	}
	printf("%.1f",a);
}
/**************************************************************
	Problem: 1303
	User: sucongyi
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/