Task: Program Execution
Input (English): b, 6, u, 7, 1, 6, U
Output (English): [['b', '6', 'u', '7', '1', '6'], ['b', '6', 'u', '7', '1', 'U'], ['b', '6', 'u', '7', '6', 'U'], ['b', '6', 'u', '1', '6', 'U'], ['b', '6', '7', '1', '6', 'U'], ['b', 'u', '7', '1', '6', 'U'], ['6', 'u', '7', '1', '6', 'U']]