Bridge

AtCoder

IDabc075_c

Time2000ms

Memory256MB

Difficulty—

You are given an undirected connected graph with $N$ vertices and $M$ edges that does not contain self-loops and double edges. The $i$\-th edge $(1 \leq i \leq M)$ connects Vertex $a_i$ and Vertex $b_i$. An edge whose removal disconnects the graph is called a _bridge_. Find the number of the edges that are bridges among the $M$ edges. ## Constraints * $2 \leq N \leq 50$ * $N-1 \leq M \leq min(N(N−1)⁄2,50)$ * $1 \leq a_i<b_i \leq N$ * The given graph does not contain self-loops and double edges. * The given graph is connected. ## Input Input is given from Standard Input in the following format: $N$ $M$ $a_1$ $b_1$ $a_2$ $b_2$ $:$ $a_M$ $b_M$ [samples] ## Notes * A _self-loop_ is an edge $i$ such that $a_i=b_i$ $(1 \leq i \leq M)$. * _Double edges_ are a pair of edges $i,j$ such that $a_i=a_j$ and $b_i=b_j$ $(1 \leq i<j \leq M)$. * An undirected graph is said to be _connected_ when there exists a path between every pair of vertices.

Samples

Input #1

Output #1

4

The figure below shows the given graph:

![image](https://img.atcoder.jp/abc075/570677a9809fd7a5b63bff11e5d9bf79.png)

The edges shown in red are bridges. There are four of them.

Input #2

Output #2

0

It is possible that there is no bridge.

Input #3

Output #3

5

It is possible that every edge is a bridge.

API Response (JSON)

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      "description_type": "Markdown"
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    "limit": {
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      "memory_limit": 262144
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    "difficulty": "None",
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    "sync_url": null,
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      "content": "You are given an undirected connected graph with $N$ vertices and $M$ edges that does not contain self-loops and double edges.  \nThe $i$\\-th edge $(1 \\leq i \\leq M)$ connects Vertex $a_i$ and Vertex $...",
      "is_translate": false,
      "language": "English"
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Full JSON Raw Segments