Dangerous bridge.

"Title description"

There are N (n <= 200) cities, where roads are built between cities, and any two cities can be directly or indirectly connected by road.

It is now asked which roads have been damaged, which will make it impossible for the two cities to connect.

"Input description"

The first line inputs two positive integers n, m (M <= 500), indicating the number of cities and the number of roads;

Next m line, each line entered two number A, B, indicating that a, b between two cities there is a road.

"Output description"

Output several lines, each containing two integers, each representing the two cities A, B (a < b) connected by the legal highway, arranged in dictionary order.

"Sample Input"

6 6

1 2

2 3

2 4

3 5

4 5

5 6

"Sample Output"

1 2

5 6

Dangerous bridge.