autofill in descending order

i was trying to autofill in descending order from 50 to 1 and i don't know how, can anyone help me?

You can enter the number 50, then enter 49 underneath it. Next, highlight both 50 and 49. Next, hover your mouse over the lower right corner of the highlighted selection until the cursor turns into a + symbol. Now, click and drag as far down as necessary to reach to 1.

Let me know if this helps.