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: '{3, 12, 13}', Set2: '{2, 8, 15, 16, 17}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output: 0

Example Input: Set1: '{5, 6, 9, 10, 11, 14, 15, 18, 19, 20}', Set2: '{2, 4}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output: 0

Example Input: Set1: '{4, 7, 8, 10, 11, 15, 16, 17}', Set2: '{2, 4, 7, 10, 13, 17, 18}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output:
4