text: # Uses python3
  
  import sys
  
  
  def move_vertex(vertex, src, dst):
      src.remove(vertex)
      dst.append(vertex)
  
  
  def acyclic(adj):
      finish = []
      current = []
      set = [x for x in range(len(adj))]
  
      def explore(v):
          move_vertex(v, set, current)
          for u in adj[v]:
              if u in finish:
                  continue
              if u in current:
                  return True
              if explore(u):
                  return True
          move_vertex(v, current, finish)
          return False
  
      while len(set) > 0:
          if explore(set[0]):
              return 1
      return 0
  
  
  if __name__ == '__main__':
      user_input = sys.stdin.read()
      data = list(map(int, user_input.split()))
      n, m = data[0:2]
      data = data[2:]
      edges = list(zip(data[0:(2 * m):2], data[1:(2 * m):2]))
      adj = [[] for _ in range(n)]
      for (a, b) in edges:
          adj[a - 1].append(b - 1)
      print(acyclic(adj))
  