Can you find all the cases where, if I put 3 balls into 2 boxes

the case is

     1     1     1
     1     1     2
     1     2     2
     2     2     2

the columns stand for a ball, the number stands for box, and the row stands for a case.

So we have 4 cases

You should write a function, input m and n, m stand for the number of balls, n stands for the number of boxes, output all the cases.

Example

If m = 3, n = 4 then you should output

     1     1     1
     1     1     2
     1     1     3
     1     1     4
     1     2     2
     1     2     3
     1     2     4
     1     3     3
     1     3     4
     1     4     4
     2     2     2
     2     2     3
     2     2     4
     2     3     3
     2     3     4
     2     4     4
     3     3     3
     3     3     4
     3     4     4
     4     4     4