# kendallr 
# Fig 33.3 
# inputs: 9 6 or 12 11

import math

def numDiscs(n,k):
  if (k == 0) or (n == 1):
    return 1
  elif k < n:
    return numDiscs(n-1, k) + numDiscs(n, k-1)
  else:
    return numDiscs(n-1,k) + numDiscs(n,k-1) - numDiscs(n-1, k-n)

n, k = map(int, input("n k=? ").split())
nds = numDiscs(n,k)
numPerms = math.factorial(n)
print("no. discordants =", nds)
print(f"p = {(nds/numPerms):.5f}")