Comparing string to number, got number

I'm trying to write a Guess My Number program and I get that error.

the code is a bit like this

guess = 0
local num = math.random(1,100)
//some prints//
guess = read()
while guess ~= num do
if guess < num then
print "Too low!
break
else
print "Too high!"
break
end
end

You need to use tonumber to turn the string into a number.

guess = tonumber( read() )