negate:
	- 0

set :A [ @++ $ @negate @-- ]

set :B [ @-- $ @++ @negate ]

test n:
	for i range 0 -- len A:
		if /= n call compose @B! i @A! i n:
			return false
	true

test to-num !prompt "Enter a number: "
if:
	!print "f^-1(f(x)) = x"
else:
	!print "Something went wrong."