# cancer 
# Fig. 33.2 
# inputs: 9 6 30

import random

NUM_TRIALS = 32000

n, min, max = map(int, input("n min max=? ").split())
perms = [i for i in range(n)]
count = 0
for m in range(NUM_TRIALS): 
  discs = 0
  random.shuffle(perms)
  for i in range(n-1):
    for j in range(i+1,n):
      if perms[i] > perms[j]:
        discs += 1
  if (discs <= min) or (discs >= max):
    count += 1
print(f"count = {count}; P = {count/NUM_TRIALS/2:.5f}")