how to calculate the difference of values (numbers) in a column?
 

A B C D
A1 10
A2 9 1
A3 8 2 1
A4 7 3 2
A5 6 4 3 1

I need to calculate the differences of each value in a column and have the
answers on second third column. For example subtract A2 from A1, A3 from A1,
A4 from A1, A5 from A1; and subtract A3 from A2, A4 from A2, A5 from A2;
subtract A4 from A3, A5 from A4; and finally subtract A5 from A4.

Any help is appreciated.