Write a function called

count_duplicates(mappings)

that takes a list of mappings (specifying a dictionary), creates the dictionary, and returns the number of values in the dictionary that appear two or more times. Recall that to create a dictionary from mappings you need the code

D = {}
for mapping in mappings:
  key = mapping[0]
  value = mapping[1]
  D[key] = value

# at this spot, outside the loop above, it's as if D was the parameter

Paste this code into the space below, then solve the problem with the dictionary D.