I have performed the XOR and the result comes as 1001. Now my confusion is that in standard S-Box (DES) the input is 6 bit where the first and last bit together specifies row and 4-middle bits column. Even if I append two zeros on the left making the XOR result 001001, then row 01 does not exist in the problem. If I don't then row 11 i.e 3 also does not exist.
The permutation table again consists of 4-bit positions suggesting the S-Box output to be represented in 4 bits(No problem in that). I am confused with the S-Box part. Please help.