Excel 2007 : Transpose multiple columns (variable) into single column (variable)

I have 400 columns and each column has unique values (cases). I want these cases to be in one variable (column) following the sequence of each case column 1 to column 400 downwards.

Supposed, I have:


A B C
1 4 7
2 5 8
3 6 9

I want these cases to look as:

A
1
2
3
4
5
6
7

How do I do this? Thank you.

I am attaching my worksheet with this query.