Task: Program Execution
Input (English): Set1: '{1, 4, 9, 11, 15, 16, 18, 19, 20}', Set2: '{4, 7, 9, 10, 11, 12, 14, 15, 17, 20}'. How many elements are there in the union of Set1 and Set2 ?
Output (English): 14