So first make sure that 20 18 is in the lower 253 lines (because line 504 is full, the remaining two positions can only be in line 505).

Another rule is found, as long as it is odd lines, the numbers increase from left to right in turn; Numbers in even lines get bigger from right to left. Therefore, in line 505, the numbers need to be arranged from right to left, so they are in line 253, column 3.