func main()
	var n: int :: cui@inputInt()
	var m: int :: cui@inputInt()
	
	var lr: []Lr :: #[m]Lr
	for i(0, m - 1)
		var l: int :: cui@inputInt()
		var r: int :: cui@inputInt()
		do lr[i] :: (#Lr).init(l, r)
	end for
	do lr.sort()
	
	var ans: int :: n
	var prev: int :: -1
	for i(0, m - 1)
		var l: int :: lr[i].l
		var r: int :: lr[i].r
		if(l <= prev & prev <= r)
		else
			do prev :: r
			do ans :- 1
		end if
	end for
	do cui@print("\{ans}\n")
	
	class Lr()
		+var l: int
		+var r: int
		+func init(l: int, r: int): Lr
			do me.l :: l
			do me.r :: r
			ret me
		end func
		+*func cmp(t: kuin@Class): int
			if(me.r < (t $ Lr).r)
				ret - 1
			elif(me.r > (t $ Lr).r)
				ret 1
			elif(me.l < (t $ Lr).l)
				ret - 1
			elif(me.l > (t $ Lr).l)
				ret 1
			else
				ret 0
			end if
		end func
	end class
end func