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

    
	
	
		
		
	

	return 0;
}

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