TPCPPLAR - Popular

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Given a directed graph G , N vertices and M arcs. 

A node X called "accessible" to Y if there is a path from X to Y

A node X called "popular" if every node Y in V fulfil one of two conditions :

1. X is accessible to Y

2. Y is accessible to X

The Problem :  Given graph G, count the number of popular node.

Input

- The first line contain N and M, the number of nodes and arcs (1 <= N <= 150000; 1 <= M <= 300000)

- M next lines, each line contains x and y, there is a arcs connect from x to y.  

Output

- First line print number of popular nodes.

- Second line print popular nodes in increasing order. 

Example

Input:

5 4

1 2

3 2

2 4

4 5

Output:

3

2 4 5


hide comments
Oleg: 2023-03-22 04:57:34

Clarification: "fulfil one of two conditions" should be read as " fulfil at least one of two conditions".


Added by:Mew.
Date:2014-09-18
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64