def  lowercase(  UpperCamelCase_					)		->  int:







 '''simple docstring'''

 # validate:
 if not isinstance(UpperCamelCase_       ,				UpperCamelCase_					) or not all(
     isinstance(UpperCamelCase_       ,				UpperCamelCase_					) and item >= 0 for item in citations					):
  raise ValueError("""The citations should be a list of non negative integers."""					)

 citations.sort()
 UpperCamelCase      =			len(UpperCamelCase_					)

 for i in range(UpperCamelCase_					):
  if citations[len_citations - 1 - i] <= i:
   return i

 return len_citations


if __name__ == "__main__":
     import doctest

     doctest.testmod()

from __future__ import annotations





def  lowercase(  UpperCamelCase_					)		->  Dict:







 '''simple docstring'''
 global graph, reversed_graph, scc, component, visit, stack
 if visit[u]:
  return
 UpperCamelCase      =			True
 for v in graph[u]:
  dfs(UpperCamelCase_					)
 stack.append(UpperCamelCase_					)





def  lowercase(  UpperCamelCase_					)		->  Optional[int]:







 '''simple docstring'''
 global graph, reversed_graph, scc, component, visit, stack
 if visit[u]:
  return
 UpperCamelCase      =			True
 component.append(UpperCamelCase_					)
 for v in reversed_graph[u]:
  dfsa(UpperCamelCase_					)





def  lowercase(  )		->  Any:







 '''simple docstring'''
 global graph, reversed_graph, scc, component, visit, stack
 for i in range(UpperCamelCase_					):
  dfs(UpperCamelCase_					)
 UpperCamelCase      =			[False] * n
 for i in stack[::-1]:
  if visit[i]:
   continue
  UpperCamelCase      =			[]
  dfsa(UpperCamelCase_					)
  scc.append(UpperCamelCase_					)
 return scc


if __name__ == "__main__":
     # n - no of nodes, m - no of edges
     _SCREAMING_SNAKE_CASE		,  _SCREAMING_SNAKE_CASE   		=			list(map(int, input().strip().split()))

     _SCREAMING_SNAKE_CASE   		=			[[] for _ in range(n)]  # graph
     _SCREAMING_SNAKE_CASE   		=			[[] for i in range(n)]  # reversed graph
     # input graph data (edges)
     for _ in range(m):
          _SCREAMING_SNAKE_CASE		,  _SCREAMING_SNAKE_CASE   		=			list(map(int, input().strip().split()))
          graph[u].append(v)
          reversed_graph[v].append(u)

     _SCREAMING_SNAKE_CASE   		=			[]
     _SCREAMING_SNAKE_CASE   		=			[False] * n
     _SCREAMING_SNAKE_CASE   		=			[]
     _SCREAMING_SNAKE_CASE   		=			[]
     print(kosaraju())
