def calculator string
  while string.match /[*\/]/
    # p string
    string.gsub!(/(\d+)\s*([*\/])\s*(\d+)/) do |regex| 
      num1 = $1.to_i
      num2 = $3.to_i
      operator = $2.to_sym
      "#{[num1, num2].reduce(operator)}"
    end
  end

  while string.match /[-\+]/
    string.gsub!(/(\d+)\s*([-\+])\s*(\d+)/) do |regex| 
      num1 = $1.to_i
      num2 = $3.to_i
      operator = $2.to_sym
      "#{[num1, num2].reduce(operator)}"
    end
  end

  string.to_i
end