Task: Program Execution
Input (English): 3831, 5649, 1757, 3567, 9697, X, V, 7575, E, 5251, 8883, S, E, 2825, 3183, 3529, U, a, X, K, 537, Y, U
Output (English): 1, 2, 3, 4, 5, 8, 10, 11, 14, 15, 16, 21