numbers = list(map(int,input().split()))
probabilities = list(map(float,input().split()))
selected_nums = list(map(int,input().split()))

prob_dict = dict(zip(numbers,probabilities))

win_prob = 1.0
for num in selected_nums:
    win_prob *= prob_dict.get(num,0)

print(f"{win_prob:.3f}")