Given a pattern containing only I's and D's. I for increasing and D for decreasing.
Devise an algorithm to print the minimum number following that pattern.
Digits from 1-9 and digits can't repeat.

Example 1:

Input:
D
Output:
21
Explanation:
D is meant for decreasing,
So we choose the minimum number
among 21,31,54,87,etc.

Example 2:

Input:
IIDDD
Output:
126543
Explanation:
Above example is self- explanatory,
1 < 2 < 6 > 5 > 4 > 3
  I - I - D - D - D

Your Task:

You don't need to read input or print anything. Your task is to complete the function printMinNumberForPattern() which takes the string S and returns a string containing the minimum number following the valid pattern.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ Length of String ≤ 8