Task: Program Execution
Input (English): 18, 21, ['6533', 'X', 'c', '9679', 'r', 'f', '9155', '1043', '9515', 'y', 'Q', '3739', '445', '267', '1575', 'M', 'E', 'C', 'B', '8671', 'Y']
Output (English): Y1768BC