from random import * 



def d6(n):

  L=[]

  for i in range(0,n):

    L.append(randrange(1,7))

  L.sort(reverse = True)

  return L



def summa(L,k):

  s = 0

  for i in range(0,k):

    s += L[i]

  return s



nopat = 4

montako = 3



#print summa(d6(nopat),montako)



S = 0

n = 10000

for i in range(0,n):

  S += summa(d6(nopat),montako)

print S*1.0/n