Given n, find count of n digit Stepping numbers. A number is called stepping number if all adjacent digits have an absolute difference of 1. 321 is a Stepping Number while 421 is not.
Input : 2
Output : 17
Explanation: The numbers are 10, 12, 21,
23, 32, 34, 43, 45, 54, 56, 65, 67, 76,
78, 87, 89, 98.
Input : 1
Output : 10
Explanation: the numbers are 0, 1, 2, 3,
4, 5, 6, 7, 8, 9.