Same code producing different result on windows and linux in ruby

I am just starting ruby. So, thought to try out some problems posted online. (here is the problem on codechef) I wrote the following piece of code:

def h(n)
    if n==0
        value = 0
   开发者_StackOverflow中文版 else
        c_n = $number[n-1].to_i
        value = ( h(n-1) * $A + c_n ) % $B
    end
    value
end

n, $A, $B, G = gets.scan(/\d+/).map! { |x| x.to_i }

(1..10**n).to_a.each {|x|
    $number = x.to_s.rjust(n, '0')
    if ( G == h(n) )
        puts $number
        break
    end
}

I compiled it on windows with the input values: 3 11 111 92

The output on windows was as expected: 084 But, on the linux machine it is: 032

What can be the possible reason? Is there anything in the given piece of code which will make the difference?

Thanks to Nakilon's comment. I got the answer.

"string"[1] = "t" in ruby 1.9 but in ruby "string"[1] = 116

So, in ruby 1.9:

c_n = $number[n-1].to_i

needs to be changed for ruby 1.8 as:

c_n = $number.split("")[n-1].to_i