General :: Transpose Multiple Rows Into A Single Column?

I need to transpose a file with over a 1000 rows of 5 columns of numbers into a file with a single column of numbers. The numbers are separated by a single space and range from one digit to 5 digits each. I tried using awk, but can only get it to grab one column of numbers.

Input:

1 2 3 4 50
600 7 8 9000 10
11 12000 13 14 15

Desired output:

1
2
3
4

[code]....

Tried using: awk '{split($0,a,""); print $NF}' <filename> and got:

50
10
15

It only grabbed the last number in each row.