Triangle Row

Have the function TriangleRow(num) take num which will be a positive integer representing some row from Pascal's triangle. Pascal's triangle starts with a [1] at the 0th row of the triangle. Then the first row is [1, 1] and the second row is [1, 2, 1]. The next row begins with 1 and ends with 1, and the inside of the row is determined by adding the k-1 and kth elements from the previous row. The next row in the triangle would then be [1, 3, 3, 1], and so on. The input will be some positive integer and your goal is to return the sum of that row. For example: if num is 4 then your program should return the sum of 1 + 4 + 6 + 4 + 1 which is 16.

Examples

Input: 1
Output: 2

Input: 2
Output: 4