#!/usr/bin/ruby
def cycle(c,m,f,h)
	return f[c] if f[c]!=nil
	q=true
	h[c].each{|e|
		if m.has_key?(e)
			q=false
		else
			m[e]=1
			q=false if !cycle(e,m,f,h)
			m.delete e
		end
	}
	f[c]=q
end
n,m=gets.split.map &:to_i
h=Hash.new{|h,k|h[k]=[]}
m.times{
g,r=gets.split.map &:to_i
gets.split.map(&:to_i).each{|e|h[g-1]<<e-1}
}
f=[nil]*n
n.times{|i|cycle(i,{i=>1},f,h)}
p f.count(true)