#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    float q;
    cin>>n;
    if(n>10){
    	q=n*2*0.9;
	}
	else {
		q=n*2.0;
	}
	printf("%.1f",q);
    return 0;
}
/**************************************************************
	Problem: 1636
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/