Task: Program Execution
Input (English): a, 4501, c, k, I, 6639, 2423, 2211, j, 8489, 3713, f, a, 6123, x, X, O, 749, 1887, q, X, 9459, o
Output (English): 1, 3, 4, 5, 9, 12, 13, 15, 16, 17, 20, 21, 23