In this task, you are given two sets, and you need to count the number of elements at the union of two given sets. A Set is shown by two curly braces and comma-separated numbers inside, like {1, 2, 3}. Union of two given sets is the smallest set which contains all the elements of both the sets. To find the union of two given sets, A and B is a set that consists of all the elements of A and all the elements of B such that no element is repeated.
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Question: Set1: '{3, 4, 5, 7, 8, 13, 16, 18, 20}', Set2: '{3, 4, 5, 6, 7, 9, 13}'. How many elements are there in the union of Set1 and Set2 ?

Answer: 11


Question: Set1: '{6, 8, 10, 12, 14, 16, 17}', Set2: '{3, 11, 13, 15, 19, 20}'. How many elements are there in the union of Set1 and Set2 ?

Answer: 13


Question: Set1: '{3, 4, 5, 6, 8, 9, 15, 17, 18}', Set2: '{9, 11, 13, 19, 20}'. How many elements are there in the union of Set1 and Set2 ?

Answer:
13