#include <bits/stdc++.h>
using namespace std;
int main(){
    int a;
    float b;
    cin>>a;
    if(a>10){
        b=a*2*0.9;
    }else{
        b=a*2;
    }
    printf("%.1f",b);
}
/**************************************************************
	Problem: 1636
	User: zhangyilei
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/