We're dividing 401604 by 3 
Let's see how many times 3 fits into 401604.

On to step 1:
If we divide 4 by 3, we get 1 and a remainder of 1.
Put 1 as the next digit of the answer. 
Result so far: 1.0
Subtracting 3 from 4 leaves us with 1.
Take the next digit (0) from the dividend and append it to 1, then repeat: 10 / 3

On to step 2:
The number 3 fits into 10 3 times, leaving a remainder of 1.
The number 3 becomes the next digit in our result. 
Result so far: 13.0
Deduct 9 from 10 and we're left with 1.
Append the next digit (1) from the dividend to 1 and continue with: 11 / 3

Going ahead to step 3:
When dividing 11 by 3, we get 3 with a remainder of 2.
Put 3 as the next digit of the answer. 
Result so far: 133.0
The remainder is 2 after subtracting 9 from 11.
Bring next digit (6) of the dividend behind the 2 and repeat the process: 26 / 3

Moving on to step 4:
If we divide 26 by 3, we get 8 and a remainder of 2.
Record the quotient 8 as the next digit in the result. 
Result so far: 1338.0
The remainder is 2 after subtracting 24 from 26.
Bring next digit (0) of the dividend behind the 2 and repeat the process: 20 / 3

Going ahead to step 5:
3 can be fit into 20 6 times, resulting in a remainder of 2.
The next digit of our result is 6. 
Result so far: 13386.0
If we subtract 18 from 20, we get 2.
Append the next digit (4) from the dividend to 2 and continue with: 24 / 3

Let's proceed to step 6:
When dividing 24 by 3, we get 8 with a remainder of 0.
The next digit of our result is 8. 
Result so far: 133868.0
If we subtract 24 from 24, we get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Let's proceed to step 7:
0 divided by 3 is 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 133868.0
Subtract 0 from 0 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Let's proceed to step 8:
3 goes into 0 0 times with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 133868.0
If we take 0 away from 0, we end up with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 133868.0, with a leftover of 0.0.