Task: Program Execution
Input (English): 13, 18, ['3119', '9831', '8457', 'X', '7723', '4471', '471', '6123', '2555', '3871', '1261', 'R', 'M', 'g', '1071', 'T', 'S', 'x', '8271', '1023', '3533', 'a']
Output (English): xST1071gM