TASK DEFINITION: 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.
PROBLEM: Set1: '{5, 6, 7, 10, 12, 13, 18, 19}', Set2: '{18, 3, 20, 15}'. How many elements are there in the union of Set1 and Set2 ?

SOLUTION: 11

PROBLEM: Set1: '{9, 10, 5, 7}', Set2: '{2}'. How many elements are there in the union of Set1 and Set2 ?

SOLUTION: 5

PROBLEM: Set1: '{1, 4, 8, 10, 18, 19, 20}', Set2: '{5, 6, 13, 14, 16, 17, 18}'. How many elements are there in the union of Set1 and Set2 ?

SOLUTION:
13