Let our mask be 1010000...000. Notice that, if we apply XOR operation to any number with this mask, the first and third bits will be complemented and all other bits will be unchanged. Since for each individual bit, XOR with 0 does not change the value of bit and XOR with 1 changes the value of bit.
Explanation:
To give a hexadecimal number, we should know the number of bits in representation of number.
