Task: Program Execution
Input (English): Set1: '{7, 11, 12, 13, 14, 15, 18, 19, 20}', Set2: '{2, 3, 4, 8, 9, 11, 13, 15, 16, 20}'. How many elements are there in the union of Set1 and Set2 ?
Output (English): 15