Given n digits from 0 to 9, you are going to combine them into a decimal number.
For example, if 2 and 9 are given, 29 and 92 are valid numbers.
However no valid number could start with 0 except 0 itself.
For example, if 2 and 0 are given, only 20 is valid while 02 is not.
This problem ask you to find a minimum number that is valid.
Noted that all digits must be used.
The first line contains a integer n. (n<=7)
The next line contains n digits.
The minimum number that is valid.