Permutation Step

Have the function PermutationStep(num) take the num parameter being passed and return the next number greater than num using the same digits. For example: if num is 123 return 132, if it's 12453 return 12534. If a number has no greater permutations, return -1 (ie. 999).

Examples

Input: 11121
Output: 11211

Input: 41352
Output: 41523