def fertile(lst):
    total = 0
    for i in range(4, 96):
        total += lst[i]
    return total

def alive(lst):
    total = 0
    for i in range(0, 96):
        total += lst[i]
    return total

def aging(lst):
    for i in range(1, 96):
        lst[96-i] = lst[95-i]

    return lst

males = [i*0 for i in range(0, 96)]
females = [i*0 for i in range(0, 96)]

males[2] = 2
females[2] = 4

Rabbits_needed_alive = 1000000000
Rabbits_total = alive(males) + alive(females)
month = 0
dead = 0

while Rabbits_needed_alive > Rabbits_total:
    month += 1
    newborn_males = fertile(females) * 5
    newborn_females = fertile(females) * 9
    males = aging(males)
    females = aging(females)
    males[0] = newborn_males
    females[0] = newborn_females
    Rabbits_total += alive(males) + alive(females)

print(month)