import java.util.*;
import java.lang.*;
import java.io.*;
class Main
{
{
Scanner in
= new Scanner
(System.
in); double n;
n=in.nextDouble();
double d;
System.
out.
printf("%.5f",
(50*(1-(Math.
pow(0.25,n
))))/(0.75)); }
}
aW1wb3J0IGphdmEudXRpbC4qOwppbXBvcnQgamF2YS5sYW5nLio7CmltcG9ydCBqYXZhLmlvLio7CgpjbGFzcyBNYWluCnsKCXB1YmxpYyBzdGF0aWMgdm9pZCBtYWluIChTdHJpbmdbXSBhcmdzKSB0aHJvd3MgamF2YS5sYW5nLkV4Y2VwdGlvbgoJewoJCVNjYW5uZXIgaW4gPSBuZXcgU2Nhbm5lcihTeXN0ZW0uaW4pOwoJCWRvdWJsZSBuOwoJCW49aW4ubmV4dERvdWJsZSgpOwoJCWRvdWJsZSBkOwoJCVN5c3RlbS5vdXQucHJpbnRmKCIlLjVmIiwoNTAqKDEtKE1hdGgucG93KDAuMjUsbikpKSkvKDAuNzUpKTsKCX0KfQ==