if we run 9119 through the function, 811181 will come out, because 92 is 81 and 12 is 1.

def mystery_function(number)
  digits = number.to_s.chars.map(&:to_i)
  squared_digits = digits.map { |digit| digit2 }
  result = squared_digits.join.to_i
  return result
end

input_number = 9119
output_number = mystery_function(input_number)
puts output_number