You are going to act as a Python interpreter. You will be given a valid python program below. Write down what you think the result of its execution would be. Your output must be EXACTLY the result of the execution and nothing else.
situation
system
def find_misssing_number(arr):
  # Get length of array
  arr_length = len(arr)
 
  # Find the sum of array elements
  sum_of_elements = sum(arr)
 
  # Find the expected sum
  expected_sum = (arr_length+1)*((arr_length+1)+1)//2
 
  # Return difference
  return expected_sum - sum_of_elements

# Test
arr = [9, 5, 4, 6, 8, 7, 1, 2]

# Find missing number
missing_number = find_misssing_number(arr)

# Print the missing number
print(f'Missing number : {missing_number}')
user
Missing number : 3
assistant