extract half a matrix

Dear all,

I'm new to matrix operations in R. I couln't find a solution to the
following problem among earlier help mails or in An introd to R, I guess
because the question is really basic.

I want to extract all above the diagonal, i.e. from

    1  2  3  4
1   0 26 49 49
2  26  0 44 40
3  49 44  0 21
4  49 40 21  0

I want

26
49
44
49
40
21

Thanks in advance!


Sincerely,
Tord