F.A.Q
Hand In Hand
Online Acmers
Problem Archive
Realtime Judge Status
Authors Ranklist

C/C++/Java Exams
ACM Steps
Go to Job
Contest LiveCast
ICPC@China
Best Coder beta
VIP | STD Contests
DIY | Web-DIY beta
Register new ID

# Necklace

Time Limit: 3000/1500 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 4421    Accepted Submission(s): 1315

Problem Description
SJX has 2*N magic gems. $N$ of them have Yin energy inside while others have Yang energy. SJX wants to make a necklace with these magic gems for his beloved BHB. To avoid making the necklace too Yin or too Yang, he must place these magic gems Yin after Yang and Yang after Yin, which means two adjacent gems must have different kind of energy. But he finds that some gems with Yang energy will become somber adjacent with some of the Yin gems and impact the value of the neckless. After trying multiple times, he finds out M rules of the gems. He wants to have a most valuable neckless which means the somber gems must be as less as possible. So he wonders how many gems with Yang energy will become somber if he make the necklace in the best way.

Input
Multiple test cases.

For each test case, the first line contains two integers $N (0 \leq N \leq 9), M (0 \leq M \leq N * N)$, descripted as above.

Then $M$ lines followed, every line contains two integers $X,Y$, indicates that magic gem $X$ with Yang energy will become somber adjacent with the magic gem $Y$ with Yin energy.

Output
One line per case, an integer indicates that how many gem will become somber at least.

Sample Input
2 1
1 1
3 4
1 1
1 2
1 3
2 1


Sample Output
1
1


Author
HIT

Source

Statistic | Submit | Discuss | Note
 Home | Top Hangzhou Dianzi University Online Judge 3.0 Copyright © 2005-2023 HDU ACM Team. All Rights Reserved. Designer & Developer : Wang Rongtao LinLe GaoJie GanLu Total 0.000000(s) query 1, Server time : 2023-06-10 01:17:14, Gzip enabled Administration