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
coolio_1:
20200305 03:00:10
AC in 1 go. Took a lot of effort. 

sangmai:
20200221 10:50:36
I believe that there are duplicated edges in test case 20. AC after handling that case. 

transonviet:
20200121 08:54:47
Wonderful prob =))) ac in one go 

swapscool:
20200117 09:23:04
Weak test cases. Getting ac by just printing vertices (sorted order) present in the scc's whose size is greater than 1. 

tanroop:
20191024 20:16:08
Which one is 20th TC. Spojtoolkit is a bit confusing 

scolar_fuad:
20190924 08:11:41
Straight forward scc 

scolar_fuad:
20190924 07:13:34
what it would be if there exist more than one ssc in a graph 

trishala_naman:
20190703 18:59:31
Input


vjvjain0:
20190528 22:55:16
Used (Kosaraju + dfs) WA on 20


nour_massri:
20190515 22:40:04
Weak Test cases my code is giving WA for this test case but it gives AC when submitted !!

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 