Task: Program Execution
Input (English): 4, ['B', '4427', '2971', '6197', 'u', 'f', '1063', 'M', 'R', 'A', '7607', '3317', '3781', 'B', 'A', 'R', '645', '4591', 'C', '7649', '8811']
Output (English): B, 4427, 2971, 6197