看看你多久能算出來?.....!

There is a bus with 7 girls inside, (車上有 7個女孩 )
Each girl has 7 bags, (每個女孩有 7個包 )
Inside each bag, there are 7 big cats, ( 每個包裡有7 只貓)
Each big cat has 7 small cats, (每只貓還有 7只小貓)
All cats have 4 Legs each! ( 每只貓都只有4條腿 )
Question: How many Legs are there inside the bus? ( 請問車上有多少條腿)
The total number of Legs would be the password for this file: ( 腿的總數是附件的密碼 )
If you can't open the file, the answer you obtained is wrong ( 如果你打不開, 證明的你的答案是錯的)

裕仁寄給我的小考題, 乍看挺簡單的, 不過 一不小心就會算錯,
難怪裕仁說他花了 3分鐘才算出來
我算的答案是 1582