Task: Program Execution
Input (English): Set1: '{3, 5, 8, 10, 11, 14, 16, 17, 19, 20}', Set2: '{3, 8, 9, 10, 11, 12, 13, 17, 19, 20}'. How many elements are there in the union of Set1 and Set2 ?
Output (English): 13