Task: Program Execution
Input (English): 4541, 4413, 1831, k, 2609, 6909, f, X, M, p, 8947, l, R, 5439, K, F, 4345, L, 3465, L, U, 7293, 4355, 3259
Output (English): 4, 7, 8, 9, 10, 12, 13, 15, 16, 18, 20, 21