In this task, you are given two sets, and you need to count the number of elements at the intersection of two given sets.  A Set is shown by two curly braces and comma-separated numbers inside, like {1, 2, 3}. The intersection of two given sets is the largest set which contains all the elements that are common to both sets. To find the intersection of two given sets, A and B is a set consisting of all the elements common to both A and B.

Example Input: Set1: '{4, 6, 9, 12, 15, 17, 18}', Set2: '{4, 8, 11, 16, 20}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output: 1

Example Input: Set1: '{2, 3, 4, 6, 8, 10, 13, 15, 17, 18}', Set2: '{5, 9, 11, 17, 18, 19, 20}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output: 2

Example Input: Set1: '{1, 13}', Set2: '{3, 4, 5, 8, 9, 10, 15, 18, 19, 20}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output:
0