Task: Program Execution
Input (English): Set1: '{1, 4, 5, 7, 8, 13, 16, 17, 19, 20}', Set2: '{2, 3, 5, 6, 9, 12, 13, 14, 18, 20}'. How many elements are there in the union of Set1 and Set2 ?
Output (English): 17