#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: zhangyilei
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/