#2.12
import random
omegaLUL = ['1']*2+['0']*8
n,m = 0,0
N = 1000000
for _ in range(N):
    new_lst = omegaLUL.copy()
    random.shuffle(new_lst)
    a = new_lst.index("1")
    new_lst[a] = "NEEDED"
    b = new_lst.index("1")
    if abs(a - b) <= 3 :
            n += 1
print(n/N)