Task: Program Execution
Input (English): Set1: '{3, 4, 5, 6, 7, 10, 13, 14, 15, 17}', Set2: '{1, 2, 3, 6, 7, 9, 12, 17, 18, 20}'. How many elements are there in the union of Set1 and Set2 ?
Output (English): 16