Task: Program Execution
Input (English): 7, 4, x, 6, 4, 1
Output (English): [['7', '4', 'x', '6', '4'], ['7', '4', 'x', '6', '1'], ['7', '4', 'x', '4', '1'], ['7', '4', '6', '4', '1'], ['7', 'x', '6', '4', '1'], ['4', 'x', '6', '4', '1']]