I'm working on UVa #112 Tree Summing. I have what I think should be a working solution but it is not accepted by the online judge due to a basic misunderstanding of the problem on my part. Consider the following inputs:

-1 (-1()())
77 (77(1()())())

or diagrammatically, the trees look like:

  -1              77
 /   \           /  \
()    ()        1    ()
               / \
              ()  ()

According to at least two working solutions, the correct output for the above inputs is:

yes
no

However, I don't understand why the second one should be 'no'. It looks to me like the rightmost path of the tree should give the proper sum. What am I missing?