- 题目提供者 洛谷
- 评测方式 云端评测
- 标签 图论 构造 POI 2013 高性能
- 难度 尚无评定
- 时空限制 1000ms / 128MB
Byteasar lives in Byteburg, a city famous for its milk bars on every corner.
One day Byteasar came up with an idea of a "milk multidrink": he wants to visit each milk bar for a drink exactly once.
Ideally, Byteasar would like to come up with a route such that the next bar is always no further than two blocks (precisely: intersections) away from the previous one.
The intersections in Byteburg are numbered from to , and all the streets are bidirectional.
Between each pair of intersections there is a unique direct route, ie, one that does not visit any intersection twice.
Byteasar begins at the intersection no. and finishes at the intersection no. .
Your task is to find any route that satisfies Byteasar's requirements if such a route exists.
An exemplary route satisfying the requirements is: There is no route that satisfies the requirements.
In the first line of the standard input there is a single integer (), denoting the number of intersections in Byteburg.
Each of the following lines holds a pair of distinct integers and (), separated by a single space, that represent the street linking the intersections no. and .
In tests worth of all points the condition holds.输出格式：
If there is no route satisfying Byteasar's requirements, your program should print a single word "BRAK" (Polish for none), without the quotation marks to the standard output. Otherwise, your program should print lines to the standard output, the -th of which should contain the number of the -th intersection on an arbitrary route satisfying Byteasar's requirements. Obviously, in that case the first line should hold the number , and the -th line - number .