If I am given a database ranging from A1:C3 in the following table, how can I set formula to derive the result as listing out in A5:A10 ? The implication for this work is that I want to show the item that appears in one time and then list them out. Those appearing in more than one time is intended to be excluded.

Column A Column B Column C
Row 1 M N K
Row 2 X U M
Row 3 K N O
Row 4
Row 5 K
Row 6 M
Row 7 N
Row 8 O
Row 9 U
Row 10 X

Kelvin