Alphabet Difference Codechef Solution

You are given two strings A and B containing small English alphabets [‘a’ – ‘z’]. You have to find the set of distinct characters that are present in string B but not in A. Print this set of characters sorted in increasing order in the form of a string.

If there are no such characters that are present in B but not in A, then print -1.

Note: You just need to print an alphabet once in the resultant string if it’s present in string B but not in string A.

Input

The first line of the input contains an integer T denoting the number of test cases. The description of T test cases follows.
First line of each testcase contains string A.
Second line of each testcase contains string B.

Output

For each test case, output a single line containing answer.

Constraints

1 ≤ T ≤ 20
1 ≤ Length of string A , B ≤ 100000

Information to Score Partial Points

For 5% of the score, it is guaranteed that Length of strings are ≤ 26 and all alphabets in string B are distinct.
For 30% of the score, it is guaranteed that Length of strings are ≤ 500.
For rest 65% of the score, original constraints are applicable.

Example
Input:
2
codechef
certification
teacher
cheater

Output:
ainrt
-1

Explanation

Test case 1: String A is “codechef” and string B is “certification”. {‘a’,’i’,’n’,’r’,’t’} are the characters present in string B but not in A.

Test case 2: String A is “teacher” and string B is “cheater”. Since all the alphabet in string B are also present in string A, hence answer is -1.

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