#include<stdio.h>
int main()
{
    double x;
    scanf("%lf",&x);
    if(x<=20)
        printf("%.2lf",1.68*x);
    if(x>20)
        printf("%.2lf",1.98*x);
        return 0;
}

/**************************************************************
	Problem: 1643
	User: admin
	Language: C
	Result: Accepted
	Time:13 ms
	Memory:1144 kb
****************************************************************/