If statement in python3

I am trying to solve a mathematics combinatorics question in python in which we select a committee of 5 people with female majority from a group of 8 men and 9 females. My code:

import random
people=["m1", "m2", "m3","m4", "m5", "m6" , "m7","m8", "l1", "l2", "l3", "l4", "l5", "l6", "l7", "l8", "l9"]
combinations=[]

for g in range(10000):
    a=random.sample(people, k=5)
    b=a.count("l1")
    b+=a.count("l2")
    b+=a.count("l3")
    b+=a.count("l4")
    b+=a.count("l5")
    b+=a.count("l6")
    b+=a.count("l7")
    b+=a.count("l8")
    b+=a.count("l9")
    if b>=3:
        if a in combinations:
            pass
        else:
            combinations.append(a)

print (len(combinations))

But for some reason this is including repeated groups. Which means my last few lines of code are not working correctly.