Codeforces celebrates 10 years! We are pleased to announce the crowdfunding-campaign. Congratulate us by the link https://codeforces.com/10years.
×

Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

E. IT Restaurants

time limit per test

1.5 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputСity N. has a huge problem with roads, food and IT-infrastructure. In total the city has *n* junctions, some pairs of them are connected by bidirectional roads. The road network consists of *n* - 1 roads, you can get from any junction to any other one by these roads. Yes, you're right — the road network forms an undirected tree.

Recently, the Mayor came up with a way that eliminates the problems with the food and the IT-infrastructure at the same time! He decided to put at the city junctions restaurants of two well-known cafe networks for IT professionals: "iMac D0naldz" and "Burger Bing". Since the network owners are not friends, it is strictly prohibited to place two restaurants of different networks on neighboring junctions. There are other requirements. Here's the full list:

- each junction must have at most one restaurant;
- each restaurant belongs either to "iMac D0naldz", or to "Burger Bing";
- each network should build at least one restaurant;
- there is no pair of junctions that are connected by a road and contains restaurants of different networks.

The Mayor is going to take a large tax from each restaurant, so he is interested in making the total number of the restaurants as large as possible.

Help the Mayor to analyze the situation. Find all such pairs of (*a*, *b*) that *a* restaurants can belong to "iMac D0naldz", *b* restaurants can belong to "Burger Bing", and the sum of *a* + *b* is as large as possible.

Input

The first input line contains integer *n* (3 ≤ *n* ≤ 5000) — the number of junctions in the city. Next *n* - 1 lines list all roads one per line. Each road is given as a pair of integers *x*_{i}, *y*_{i} (1 ≤ *x*_{i}, *y*_{i} ≤ *n*) — the indexes of connected junctions. Consider the junctions indexed from 1 to *n*.

It is guaranteed that the given road network is represented by an undirected tree with *n* vertexes.

Output

Print on the first line integer *z* — the number of sought pairs. Then print all sought pairs (*a*, *b*) in the order of increasing of the first component *a*.

Examples

Input

5

1 2

2 3

3 4

4 5

Output

3

1 3

2 2

3 1

Input

10

1 2

2 3

3 4

5 6

6 7

7 4

8 9

9 10

10 4

Output

6

1 8

2 7

3 6

6 3

7 2

8 1

Note

The figure below shows the answers to the first test case. The junctions with "iMac D0naldz" restaurants are marked red and "Burger Bing" restaurants are marked blue.

Codeforces (c) Copyright 2010-2020 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Feb/18/2020 23:21:44 (g2).

Desktop version, switch to mobile version.

Supported by

User lists

Name |
---|