Topic: !!!Pleeeease Help!!!

I just started to teach myself ruby as a first language from Chris Pines's book. There is a exercise to write a program that will translate arabic numbers to old style roman numbers.
I have completed the exercise and my code is works but only if I type in numbers that are not divisible by 5. As soon I type in a number divisible by 5 I get the following error: No implicit conversion from nil to integer (Type error)
I completely stuck.
I would be really grateful if someone could look at my code and explain what am I doing wrong.
puts 'Please type in a number that you would like to be translated'
puts 'to old style Roman number:'

def romnum leftover
    var_i = 'I'
    var_v = 'V'
    var_x = 'X'
    var_l = 'L'
    var_c = 'C'
    var_d = 'D'
    var_m = 'M'
       
    leftover = ''
       
    leftover = gets.chomp
   
    numb_m  = leftover.to_i / 1000
    leftover = leftover.to_i % 1000
   
    if leftover != 0
        numb_d = leftover / 500
        leftover = leftover % 500
       
        if leftover != 0
            numb_c = leftover / 100
            leftover = leftover % 100
           
            if leftover != 0
                numb_l = leftover / 50
                leftover = leftover % 50
               
                if leftover != 0
                    numb_x = leftover /10
                    leftover = leftover % 10
                   
                    if leftover != 0
                        numb_v = leftover / 5
                        leftover = leftover % 5
                       
                        if leftover != 0
                            numb_i = leftover /1
                            leftover = 0
                        end
                    end
                end
            end
        end
    end
   
   
    puts var_m * numb_m + var_d * numb_d + var_c * numb_c + var_l * numb_l + var_x * numb_x + var_v * numb_v + var_i * numb_i
end


romnum 5

Re: !!!Pleeeease Help!!!

You should probably ask this at http://www.ruby-forum.com/

Just because this isn't Rails based at all.