Task: Program Execution
Input (English): Set1: '{2, 3, 4, 5, 6, 7, 9, 16, 17, 18}', Set2: '{2, 3, 5, 7, 8, 10, 11, 16, 17, 18}'. How many elements are there in the union of Set1 and Set2 ?
Output (English): 13