include <stdio.h>

include <math.h>

int main() {

double a,b,c,d,e;
scanf("%lf",&a);
b=ceil(a);
if(a<=20)
{
    c=b*1.68;
    printf("%.2lf",c);
}
else
{
    d=(b-20)*1.98;
    e=20*1.68+d;
    printf("%.2lf",e);
}
return 0;

}