func main()
	var n: int :: cui@inputInt()
	var m: int :: cui@inputInt()
	var dic: dict<int, bool> :: #dict<int, bool>
	for(1, m)
		var u: int :: cui@inputInt()
		var v: int :: cui@inputInt()
		do dic.add(v, true)
	end for
	
	var ans: int :: n - ^dic
	do cui@print("\{ans}\n")
end func