fix this `class grains def self.square(n) = 2 ** (n - 1); raise argumenterror if !n.between?(1,64) def self.total = 18_446_744_073_709_551_615 end` in ruby

To fix the syntax error and argument error in the given Ruby code, you can make the following adjustments:

main.rb
class Grains
  def self.square(n)
    raise ArgumentError, 'Invalid input' unless n.between?(1, 64)
    2**(n - 1)
  end

  def self.total
    (1..64).sum { |n| square(n) }
  end
end
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Here's what has changed:

1. The class name grains was changed to Grains. By convention, class names in Ruby should be written in camel case with the first letter capitalized.
2. The syntax error in the square method was corrected. The = sign was replaced with def. Additionally, the indentation and spacing were adjusted for improved readability.
3. An ArgumentError is raised when the input n is not between 1 and 64. This ensures that only valid inputs are accepted.
4. The total method was corrected to calculate the sum of squares for all positions on the chessboard (from 1 to 64). The sum method, combined with a range, is used to calculate the total number of grains.

Please note that the calculation for the total method assumes that you want to calculate the total number of grains for all squares on a chessboard using the doubling strategy (starting with 1 grain on the first square). Adjust the calculation inside total if the intended logic is different.

Now the code should be free of syntax errors and handle invalid input correctly.