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: '{1, 2, 5, 7, 8, 11, 12, 13, 17}', Set2: '{7, 10, 13, 14, 16, 17}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output: 3

Example Input: Set1: '{9, 10, 12, 13, 16}', Set2: '{2, 4}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output: 0

Example Input: Set1: '{2, 6, 7, 12, 13, 15, 17}', Set2: '{4, 6, 10, 11, 13, 15, 16, 17, 18, 19}'. How many elements are there in the intersection of Set1 and Set2 ?
Example Output:
4