Imagine you have a special keyboard with the following keys: Key 1: (A): Print one 'A' on screen. Key 2: (Ctrl-A): Select the whole screen. Key 3: (Ctrl-C): Copy selection to buffer. Key 4: (Ctrl-V): Print buffer on screen appending it after what has already been printed. Now, you can only press the keyboard for N times (with the above four keys), find out the maximum numbers of 'A' you can print on screen. Example 1: Input: N = 3 Output: 3 Explanation: We can at most get 3 A's on screen by pressing following key sequence: A, A, A Example 2: Input: N = 7 Output: 9 Explanation: We can at most get 9 A's on screen by pressing following key sequence: A, A, A, Ctrl A, Ctrl C, Ctrl V, Ctrl V Note: 1 <= N <= 50 Answers will be in the range of 32-bit signed integer.