Merging 2 Columns Into 1 Alternating Every Other Column

I'm looking for a way to put data into 1 column from 2 different columns, alternating every other row.

The data looks like this:
A B C
1 2
3 4
5 6

And I want C to look like this:
C
1
2
3
4
5
6

I don't necessarily need to keep the data in columns A and B, as long as C follows this format.

Excellent, just what I was looking for. I couldn't get the UDF working right, I'll try messing around with it, but the Index solution works great!