題目描述
Every year,prince prepares a birthday gift for princess.The gift is a box,which is decorated with jewel.
As princess grows older,the level of the jewelry box gradually increase from A to Y.
Every level N jewelry box will be packed in level (N-1) jewelry box(except level 1 jewelry box).
For example,when princess was 1 year old,she got a level-A (level 1) jewelry box.When pricess was 2 years old,she got a level-B(level 2) jewelry box.The level-B(level 2)jewelry box was packed in level-A(level 1) jewelry box.
Because prince has obsessive-compulsive disorder, there will be a paper box between two jewelry box.
Please help prince to determine the birthday gift.