You are given two very large numbers made up of 1 or 0 only. You have to find the digit by digit XOR of the two numbers, i.e., the i-th digit of the answer is 1 if and only if the i-th digit of the two given numbers differ otherwise the i-th digit of the answer is 0. The number of digits in both the numbers is same.

Input:

First line contains the number of test cases T.

Each test case is represented by two lines representing the two numbers. It is guaranteed that the numbers are made from 0 and 1 only and that their length is same.

Output:

For each test case print the corresponding answer.

Constraints:

1 ≤ T ≤ 100

1 ≤ Number of digits in a number ≤ 10^4

SAMPLE INPUT
2
01110
01100
010
111

SAMPLE OUTPUT
00010
101

见题面

见题面