def consecutive_lists(num)
  list_of_sub_lists = []
  digit_list = num.to_s.split("")
  start_index = 0
  end_index = 4
  while end_index < digit_list.size
    list_of_sub_lists << digit_list[start_index..end_index].map(&:to_i)
    start_index += 1
    end_index += 1
  end
  list_of_sub_lists
end

def consecutive_products(num)
  product_list = []
  consecutive_lists(num).each do |list|
    product_list << list.inject(:*)
  end
  product_list
end

def largest_consecutive_product(num)
  consecutive_products(num).max
end

puts largest_consecutive_product(7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450)