When calculating the division vertically, start with the most significant bit. If it can't be divided, then the highest bit and the next bit are combined into a number to divide until the divisor can be divided.

Law of integer division:

1) Start with the high order of the dividend, first look at how many digits there are in the dividend, and then try to divide the dividend by the first few digits. If it is less than the divisor, try dividing it by one digit.

2) Write the quotient except the dividend on the dividend.

3) The remainder after each division operation must be less than the divisor.