do
	clear screen
	n$=""
	for i=1 to 4
		n$=n$+str$(int(ran(9)+1))
	next i
	print at(35,0) "24 GAME\n"
	print "Combine numbers and operators for obtain 24."
	print "Allowed characters: ";
	i$=n$+"+-*/()"
	for i=1 to 10
		print mid$(i$,i,1)," ";
	next i
	print "[nothing to end program]\n"
label accept
	p$=""
	i$=n$+"+-*/()"
	print at(0,4);:input "Enter the formula: " f$
	if f$="" end
	for i=1 to len(f$)
		c$=mid$(f$,i,1)
		switch c$
			case " ": f$=left$(f$,i-1)+right$(f$,len(f$)-i): break
			case "+":case "-":case "*":case "/": p$=p$+"o": break
			case "(":case ")": p$=p$+c$: break
			case mid$(i$,1,1): p$=p$+"n": mid$(i$,1,1)=" ": break
			case mid$(i$,2,1): p$=p$+"n": mid$(i$,2,1)=" ": break
			case mid$(i$,3,1): p$=p$+"n": mid$(i$,3,1)=" ": break
			case mid$(i$,4,1): p$=p$+"n": mid$(i$,4,1)=" ": break
			default: message(" = Invalid argument!  "): break
		end switch
		if f$="" goto accept
	next i
	restore
	for i=1 to 11
		read t$
		if t$=p$ break
	next i
	if t$<>p$ then
		message(" = Bad construction!  ")
		goto accept
	end if
	let r=eval(f$)
	print "\n",f$," = ",r," ";
	if r<>24 then
		message(" = Wrong!             ")
		goto accept
	else
		message(" = Correct!           ")
		pause 5
	end if
loop

DATA "nononon"
DATA "(non)onon"
DATA "nono(non)"
DATA "no(no(non))"
DATA "((non)on)on"
DATA "no(non)on"
DATA "(non)o(non)"
DATA "no((non)on)"
DATA "(nonon)on"
DATA "(no(non))on"
DATA "no(nonon)"

sub message(m$)
	print at(0,7) f$,m$
	beep: beep: beep
	pause 1
	print at(19,4) "                     "
	f$=""
end sub

sub eval(c$)
	static linea
	
	linea=linea+1
	c$="sub s"+str$(linea+1000000,"#######")+"():return "+c$+":end sub"
	compile c$
	return execute(mid$(c$,5,8))
end sub