#include<stdio.h>
int main()
{
    int x;
    scanf("%d",&x);
    if(x<=10)
        printf("%.1lf",2.0*x);
    if(x>10)
        printf("%.1lf",1.8*x);
        return 0;
}
/**************************************************************
	Problem: 1636
	User: admin
	Language: C
	Result: Accepted
	Time:12 ms
	Memory:1144 kb
****************************************************************/