Finding duplicate values in dictionary and print Key of the duplicate element

What can be the fastest way to to check the duplicate values in the dictionary and print its key?

Dictionary MyDict which is having following values,

Key Value

22 100

24 200

25 100

26 300

29 200

39 400

41 500

Example: key 22 and 25 have same values and i need to print that 22 and 25 have duplicate values.