#include<bits/stdc++.h>
using namespace std; 
int main(){
    int n;
    cin>>n;
    if(n>=10){
        printf("%.1f",2.0*n);
    }else{
        printf("%.1f",2.2*n);
    }
    return 0;
}
 
/**************************************************************
	Problem: 1303
	User: panjinyan
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/