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
aditya_305:
20190515 07:21:24
Long implemention !! 

great_coder1:
20190329 10:59:16
What do we mean by candidate cities


az2019:
20190323 09:54:59
B_U_T_ful


ameernsr:
20190323 08:10:30
badihijat!


malish_228:
20190304 18:27:38
GG easy scc + dfs 

lamia2658:
20190203 07:30:36
the nodes which are involved in an SCC whose size is > 1 is the answer. Dont forget to sort the answer before submitting ;)


paras meena:
20181125 21:58:36
Time constraint for java is not added properly. Converted same TLE java code in C++ and got AC.


ashishgup:
20180918 22:44:31
20th test case for me was not printing the cities in increasing order :( 

preet_t:
20180829 08:09:23
can also be solved using Kosaraju's algo. 

m__sharma:
20180814 09:58:49
TLE even after using TARJAN ! any hint?

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 