# http://c...content-available-to-author-only...e.com/questions/1209/calculate-probability-of-getting-half-as-many-heads-as-coin-tosses/51443#51443
# len = 99
from itertools import*
n=int(input())
print(sum(n/2==i.count("H")for i in product(*["HT"]*n))/2**n)
IyBodHRwOi8vYy4uLmNvbnRlbnQtYXZhaWxhYmxlLXRvLWF1dGhvci1vbmx5Li4uZS5jb20vcXVlc3Rpb25zLzEyMDkvY2FsY3VsYXRlLXByb2JhYmlsaXR5LW9mLWdldHRpbmctaGFsZi1hcy1tYW55LWhlYWRzLWFzLWNvaW4tdG9zc2VzLzUxNDQzIzUxNDQzCiMgbGVuID0gOTkKCmZyb20gaXRlcnRvb2xzIGltcG9ydCoKbj1pbnQoaW5wdXQoKSkKcHJpbnQoc3VtKG4vMj09aS5jb3VudCgiSCIpZm9yIGkgaW4gcHJvZHVjdCgqWyJIVCJdKm4pKS8yKipuKQ==