isBalanced: function [s][
	cnt: 0

	loop split s [ch][
		if? ch="]" [
			cnt: cnt-1
			if cnt<0 -> return false
		]
		else [
			if ch="[" -> cnt: cnt+1
		]
    ]

    cnt=0
]

loop 1..10 'i [
	str: join map 0..(2*i)-1 [x][ sample ["[" "]"]]
	
	prints str

	if? isBalanced str  -> print " OK"
	else 				-> print " Not OK"
]