def nawiasy(xs: List[Char]): List[Char]={
	if(xs==Nil) return Nil
	else{
		if(xs.head=='(' || xs.head==')') return xs.head::nawiasy(xs.tail)
		else return nawiasy(xs.tail)
	}
}

def zliczanie(x: Int, xs: List[Char]): Int = {
	if(xs==Nil) return x
	else{
		if(x<0) return x
		else{
			if(xs.head=='(') return zliczanie(x+1,xs.tail)
			else return zliczanie(x-1,xs.tail)
		}
	}
}

def setZero(): Int = 0

def balance(xs: List[Char])= zliczanie(setZero(),nawiasy(xs))==0