When 392 is divided by 256, quotient is 1 and the remainder is 136.
When 256 is divided by 136, quotient is 1 and the remainder is 120.
When 136 is divided by 120, quotient is 1 and the remainder is 16.
When 120 is divided by 16, quotient is 7 and the remainder is 8.
When 16 is divided by 8, quotient is 2 and the remainder is 0.
So the HCF = 8