from random import choice
omega = [('g','r')]*12 + [('g','g')]*3
n, N, m = 0, 1000000, 0
for i in range(N):
    z = choice(omega)
    a = False
    for i in range(6):
        if choice(z) == 'r':
            a = False
            break
        a = True
    if a == True:
        m+=1
    if a == True and z == ('g','g'):
        n+=1
print(n/m)