Task: Program Execution
Input (English): 21, 24, ['X', '1873', '1859', '479', '6495', 'R', '8691', '9423', '8125', '7479', 'a', '7605', 'l', '4437', 't', 'z', 'S', '7567', 'z', 'a', 'T', 'E', 'Y', '6879', 'e', 'c', 'f']
Output (English): 6879