CAPCITY  Capital City
There are N cities in Flatland connected with M unidirectional roads. The cities are numbered from 1 to N. The Flat Circle of Flatland (FCF) wants to set up a new capital city for his kingdom. For security reasons, the capital must be reachable from all other cities of Flatland. FCF needs the list of all candidate cities. You are the chief programmer at FACM (Flat Association for Computing Machinery) responsible for providing the list to FCF as soon as possible.
Input
The first line of the input file contains two integers: 1 ≤ N ≤ 100,000 and 1 ≤ M ≤ 200,000. Each of the following M lines contains two integers 1 ≤ A, B ≤ N denoting a road from A to B.
Output
The output file contains an integer denoting the number of candidate cities followed by the list of candidate cities in increasing order.
Example
Input: 4 4 1 2 3 2 4 3 2 1 Output: 2 1 2
hide comments
Archit Jain:
20141203 16:41:40
nice one!


Sumit:
20141202 22:18:16
Guys take care about the increasing order condition cost me 5 wa's 

vishal:
20141130 07:04:30
wa on 20th test case..!!


Ankur Singh:
20141111 12:08:48
nice problem ... taught me kernel DAG


Ayush Vatsa:
20141031 07:16:01
very weak test cases.....wrong algorithm is getting accepted 

mohsin mohammad:
20140815 21:25:29
Easy graph problem.... 

Adarsh Mohata:
20140615 10:59:42
Exactly same problem as TOUR..just need to change the constraints.Also,the test cases are very weak compared to TOUR Last edit: 20140615 11:00:33 

Pratik kumar:
20140204 19:29:55
weak test cases :(


cegprakash:
20140106 12:18:32
There is no test case in which there is no capital city. Add it plz.. Last edit: 20160729 22:20:13 

npsabari:
20140114 08:14:39
Simple one, given you know about the maximal connected subgraphs! 
Added by:  Narek Saribekyan 
Date:  20100620 
Time limit:  1s4s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: NODEJS OBJC PERL6 SQLITE VB.NET 
Resource:  Armenian TST 2010, Round 2 