old_contents: def solution(nums):
  	n = len(nums) + 1
  	sums = 0
  	Summation = 0
  	for i in nums:
  		sums += i
  	for i in xrange(0,n+1):
  		Summation += i
  	return (Summation - sums) % n
new_contents: def solution(nums):
  	n = len(nums) + 1
  	sums = 0
  	Summation = 0
  	for i in nums:
  		sums += i
  	for i in xrange(0,n+1):
  		Summation += i
  	return (Summation - sums) % n
  
subject: Update solution.py