XOR Encryption Key Determination

You are given a number of encryption tasks. Each task consists of an original binary message and its corresponding ciphertext, both having the same length. The encryption key is determined by performing a bitwise XOR operation between the two binary strings.

The XOR operation on binary digits is defined as follows: for each bit position, if the bits are different, the resulting bit is 1; if they are the same, the resulting bit is 0. In mathematical terms, if \(M\) is the original message and \(C\) is the ciphertext, then the key \(K\) is given by:

\(K = M \oplus C\)

Your task is to compute the encryption key for each test case and output the result.

inputFormat

The input consists of multiple test cases. The first line contains a single integer \(T\) representing the number of test cases. Each test case is described in one line with the following format:

N message ciphertext

where:

• \(N\) is an integer denoting the length of the binary strings.
• message is the original binary string.
• ciphertext is the encrypted binary string.

Both binary strings are of equal length \(N\).

outputFormat

For each test case, output a single line containing the encryption key. The encryption key is the bitwise XOR of the original message and the ciphertext.

## sample

2
4 1010 1101
3 011 101

0111
110

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