N=int(input())
if N%2==0:
  print(float(1/2))
else:
  print(float(1-(N-1)/2/N)) N=int(input()) N int(input()) int input() input if N%2==0:
  print(float(1/2))
else:
  print(float(1-(N-1)/2/N)) N%2==0 N%2 N 2 0 print(float(1/2)) print float(1/2) float 1/2 1 2 print(float(1-(N-1)/2/N)) print float(1-(N-1)/2/N) float 1-(N-1)/2/N 1 (N-1)/2/N (N-1)/2 N-1 N 1 2 N N=int(input()) int(input()) N
N=int(input())
if N%2==0:
  print(float(1/2))
else:
  print(float(1-(N-1)/2/N))
