Question 12
Hà has four stickers numbered 1, 2, 3 and 4 as shown. Hà places sticker 3 on sticker 4, then sticker 2 on sticker 3, and finally sticker 1 on sticker 2, aligning the squares marked $X$ and $Y$ on all four stickers exactly. How many of the digits 4 on sticker 4 are covered by stickers 1, 2 and 3?
