Write a Python program to print the key of the element in a dictionary that has the maximum value.
{'a': 3, 'b': 6, 'c': 9, 'd': 12}
dictionary = {'a': 3, 'b': 6, 'c': 9, 'd': 12}

max_value = max(dictionary.values())
for key, value in dictionary.items():
 if value == max_value:
 print(key)