import random
omega = ['w','w','w','w','w','w','w','w','m','m','m','m','m','m','m','m','m']
n,m = 0,0
N = 10000
for i in range(N):
    a = []
    for i in range(7):
        a += [random.choice(omega)]
    if a.count('w') == 4:
        n+=1
print(n/N)