code: def missing_number(nums):
      s = sum(nums)
      n = len(nums) + 1
      # sum formula (sum of the first n numbers) = (N*(N+1))/2
      return n * (n + 1) // 2 - s
  
label_desc: Use image node_id 1 for calling a global function with example usage: missing_number(nums) and returns: unknown